Impact of obstructive sleep apnea severity and treatment on COVID-19 vaccine-induced immune responses

Abstract

Background

Obstructive sleep apnea (OSA) is a common disorder linked to immune dysregulation and increased risk of severe coronavirus disease 2019 (COVID-19) outcomes. While vaccination is essential for preventing infection and severe disease, the impact of OSA on vaccine efficacy remains underexplored. This study examines the effects of OSA on immune responses following the third dose of the inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine (CoronaVac or BBIBP-CorV).

Methods

A total of 97 severe OSA participants with apnea-hypopnea index (AHI) >30 events/hour, and 88 healthy donors (HDs) were enrolled. Among the OSA participants, 43 individuals without symptomatic treatment before and during follow-up were designated as the untreated OSA group, while 41 participants receiving positive airway pressure (PAP) prior to the third COVID-19 vaccine dose were categorized as the treated OSA group. Full-night polysomnography (PSG) was performed to assess OSA severity. Neutralizing antibody (nAb) levels and cellular immune responses were analyzed at multiple time points following booster vaccination.

Results

Immune responses in untreated OSA participants were inversely associated with disease severity. Specifically, untreated OSA participants with AHI >50 events/hour exhibited significantly reduced nAb titers, antibody-secreting cell (ASC) frequencies, and circulating T follicular helper (cTfh) cells, indicating impaired immune recall responses. In contrast, PAP-treated OSA participants demonstrated improved humoral responses, notably at peak immune response stages.

Conclusions

These findings highlight a severity-dependent impairment of vaccine-induced immune responses in untreated OSA participants, with evidence that PAP treatment may enhance vaccine efficacy. This study emphasizes the need to consider OSA severity and treatment when optimizing vaccination strategies for this population.

Highlight box.

Key findings

• We revealed an inverse correlation between obstructive sleep apnea (OSA) severity and immune response in untreated patients, with those exhibiting an apnea-hypopnea index >50 events/hour showing notably lower neutralizing antibody (nAb) titer, antibody-secreting cell, circulating T follicular helper (cTfh), and CD40L⁺ cTfh, while positive airway pressure (PAP)-treatment enhanced nAb titer in patients with severe OSA.

What is known and what is new?

• Patients with OSA had heightened risk of severe coronavirus disease 2019 (COVID-19) outcomes. Vaccination was crucial for preventing infection and severe disease, while the effects of OSA on immune responses following COVID-19 vaccination require further clarification.

• We found that OSA decreases vaccine immune response in a disease severity-dependent manner and PAP treatment plays a positive effect on humoral immunity.

What is the implication, and what should change now?

• The results highlight the necessity of accounting for OSA severity and the potential advantages of PAP treatment within vaccination strategies. We propose that PAP treatment should be given more consideration to enhance vaccine efficacy in patients with severe OSA.

Introduction

Obstructive sleep apnea (OSA) is a common sleep disorder linked to obesity and structural airway abnormalities. It is marked by recurrent upper airway collapses during sleep, causing chronic intermittent hypoxia (IH) and sleep fragmentation (SF) (1). Severe OSA is associated with impaired oxygenation, typically assessed using indices such as the apnea-hypopnea index (AHI), oxygen desaturation index (ODI), lowest oxygen saturation (LSpO₂), percentage of sleep time with oxygen saturation (SpO₂) below 90% (T90), and the proportion of time with SpO₂ below 90% relative to total recording time (C90) (2). Global prevalence estimates of OSA vary from 9% to 38% across various regions and populations (1-5). OSA not only impairs life quality but also poses numerous health risks, including excessive daytime sleepiness, increased risk of motor vehicle accidents, depression, cardiovascular diseases (6,7), metabolic dysregulation (8,9), and neurocognitive disorders (10,11). These health impacts collectively contribute to a substantial economic burden (12).

The underlying pathogenicity of OSA is related to chronic immune dysregulation (13-15), which is associated with an increased susceptibility to infections, including influenza (16), respiratory syncytial virus (RSV) (17), human immunodeficiency virus (HIV) (18), and notably severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (19,20). The higher incidence of severe coronavirus disease 2019 (COVID-19) outcomes in OSA participants, such as increased rates of hospitalization (19), intensive care unit admission (20,21), mortality (22,23), and post-acute sequelae (24,25), underscores the particular vulnerability of this population during the SARS-CoV-2 pandemic.

Vaccination plays a crucial role in preventing infection and severe disease. However, the safety and efficacy of COVID-19 vaccination specifically in OSA participants remain underexplored. A study involving 122 older OSA participants of varying severity levels found that COVID-19 vaccination efficacy, measured by anti-SARS-CoV-2 immunoglobulin G (IgG) levels post-vaccination, was consistent across mild to severe OSA cases (26). Similar findings were reported by Dopp et al., who observed comparable serum antibody titers between moderate-to-severe OSA participants and healthy donors (HDs) following influenza immunization (27). However, both studies focused exclusively on humoral immune responses at a single time point, overlooking cellular immune responses and failing to track immune dynamics. The impact of OSA severity on the levels and dynamics of immune responses following COVID-19 vaccination in diverse aged groups remained unclear.

Positive airway pressure (PAP) is a critical intervention for mitigating the impact of chronic IH and SF on the immune system in OSA participants (28-30). PAP has been shown to reduce hospitalization rates for acute influenza in OSA participants (16). Yet, its effect on vaccine immunization outcomes remains poorly understood.

In this study, we conducted multiple timepoints analyses of serum and peripheral blood mononuclear cells (PBMCs) to assess humoral and cellular immune responses before and after the third dose of an inactivated COVID-19 vaccine (CoronaVac or BBIBP-CorV) in participants with severe OSA, with and without PAP treatment, alongside HDs. Besides, a questionnaire was designed and collected related to the adverse reactions post-vaccination to evaluate the safety of the COVID-19 vaccines. Our findings aim to provide insights into immune responses following vaccination in participants with OSA. We present this article in accordance with the STROBE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-391/rc).

Methods

Human ethics approval

The study was approved by the Medical Ethics Committee of the First Affiliated Hospital of Guangzhou Medical University (No 2021-78). Written informed consents were obtained from participants. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments.

Participants recruitment and clinical parameters acquisition

The participant recruitment and sample collection were conducted between October 2021 and August 2022. Eligible participants were aged 18–65 years, had received the third dose of inactivated SARS-CoV-2 vaccines (including CoronaVac and BBIBP-CorV), and had been diagnosed with severe OSA based on full-night polysomnography (PSG) performed at the First Affiliated Hospital of Guangzhou Medical University within the past 3 years. Volunteers with history of SARS-CoV-2 infection, receipted of other types of SARS-CoV-2 vaccines, currently taking systemic medications (e.g., glucocorticoids, immunosuppressants) were excluded. The comorbidity of the volunteers is shown in Table 1. To analyze the effect of the most common treatment PAP on vaccine immune responses, OSA participants with other treatment (oral appliance, nasopharyngeal surgery, etc.) were excluded. Besides, healthy volunteers were also recruited as control. Their essential information, comorbidities, COVID-19 vaccine brands and doses, as well as administration times (Table 1), and adverse reactions following vaccination were collected via questionnaires (Table 2). To re-clarify the diagnosis and severity of OSA, the PSG was performed again 1 week before enrollment in the sleep center (Philips Respironics, Murrysville, PA, USA) at the First Affiliated Hospital of Guangzhou Medical University, according to the recommendations of the American Academy of Sleep Medicine (AASM) guide (31,32). On the basis of pre-enrollment PSG results, severe OSA participants with AHI >30 events/hour was finally included in our study. AHI, ODI, LSpO₂, T90, and C90 were recorded from the PSG report before the first blood sampling. Participants treated with PAP were required to provide their treatment chip records from their PAP devices.

Table 1. Characteristics of participants.

Parameters	OSA (n=97)	HD (n=88)	P value
Basic information
Male	93 (95.9)	83 (94.3)	0.62
Age (years)	42 [37–46]	38 [32–48]	0.055
BMI (kg/m2)	27.5 [25.6–30.4]	23.6 [21.8–26.1]	<0.001
Comorbidities
Hypertension	27 (27.8)	0	<0.001
Diabetes/hyperglycemia	3 (3.1)	0	0.10
Hyperlipidemia	1 (1.1)	0	0.34
Hyperthyroidism	4 (4.1)	0	0.054
Hyperuricemia/gout	6 (6.2)	0	0.02
Rhinitis	4 (4.1)	0	0.054
Vaccines information
Vaccine manufacturer (1st dose)
CoronaVac	59 (60.8)	3 (3.4)	<0.001
BBIBP-CorV	38 (39.2)	85 (96.6)	<0.001
Vaccine manufacturer (2nd dose)
CoronaVac	66 (68.0)	9 (10.2)	<0.001
BBIBP-CorV	31 (32.0)	79 (89.8)	<0.001
Vaccine manufacturer (3rd dose)
CoronaVac	58 (59.8)	9 (10.2)	<0.001
BBIBP-CorV	39 (40.2)	79 (89.8)	<0.001
Days interval between vaccine doses
1st to 2nd	31 [25–36]	29 [28–34]	0.97
2nd to 3rd	188 [184–198]	218 [188–226]	<0.001
Injection with single brand from 1st to 3rd dose	65 (67.0)	82 (93.2)	<0.001
CoronaVac	46 (70.8)	3 (3.7)	<0.001
BBIBP-CorV	19 (29.2)	79 (96.3)	<0.001
Injection with mixed two brands from 1st to 3rd dose	32 (33.0)	6 (6.8)	<0.001

Data are presented as median [IQR], or n (% of parent). Mann-Whitney unpaired t-test and the Chi-squared test were used respectively to compare the differences between groups. BMI, body mass index; HD, healthy donor; IQR, interquartile range; OSA, obstructive sleep apnea.

Table 2. Adverse events within 7 days post third vaccine dose.

Adverse events	OSA (n=69)†	HD (n=85)†	P value
Systemic
Fatigue	11 (15.9)	10 (11.8)	0.45
Myalgia	16 (23.2)	12 (14.1)	0.15
Headache	3 (4.3)	1 (1.2)	0.22
Anorexia	1 (1.4)	1 (1.2)	0.88
Nausea	1 (1.4)	1 (1.2)	0.88
Fever	2 (2.9)	1 (1.2)	0.44
Injection-site
Pain	46 (66.7)	44 (51.8)	0.06
Swelling	5 (7.2)	4 (4.7)	0.50
Itching	6 (8.7)	2 (2.4)	0.08
Redness	0	1 (1.2)	0.37
Hypoesthesia/induration	1 (1.4)	0	0.27

Data are presented as n (%). ^†, adverse events information of 28 OSA participants and 3 HDs were not acquired. Chi-squared test was used to compare the differences between groups. HD, healthy donor; OSA, obstructive sleep apnea.

Criteria for OSA grouping

To better understand the influence of OSA and the effect of PAP on vaccine immunity, two groups of participants with severe OSA were picked out for further analysis (Table 3), those without PAP or any symptomatic treatment before and during our follow-up period were marked as the untreated group (n=43), while who start PAP treatment prior to their third vaccination, regardless of the duration of treatment, according to the usage record from PAP were classified as the treated group [n=41, median days of PAP treatment to third vaccination: 364 (range, 99–823)]. Participants with OSA who start PAP treating post the third booster vaccination (n=7) and who undergone other treatments or couldn’t provide the PAP records for some force majeure factors (n=6) were marked out, because their PAP treatment initiation timing were uncertain.

Table 3. PSG parameters of participants with OSA.

Parameters	Total OSA		Untreated			Start PAP treatment before 3rd vaccination
	AHI >30 (n=97)		30< AHI ≤50 (n=20)	AHI >50 (n=23)		30< AHI ≤50 (n=17)	AHI >50 (n=24)
AHI†	52.0 (40.0–64.9)		38.8 (33.5–44.5)	61.7 (54.5–69.3)***		38.7 (34.8–40.9)	64.8 (54.1–74.1)###
LSpO2 (%)	70.0 (64.0–77.0)		75.5 (69.8–80.3)	65.0 (62.5–71.0)**		77 (68.5–79.5)	66.0 (62.0–73.0)##
T90 (%)	17.4 (7.0–34.8)		7.1 (4.5–9.5)	30.8 (16.3–42.3)***		6.8 (5.3–11.4)	31.1 (17.6–37.3)###
C90 (%)	12.8 (5.8–29.4)		5.4 (3.9–7.5)	26.0 (13.0–34.5)***		5.9 (4.8–10.4)	27.8 (14.2–34.7)###
ODI†	54.3 (42.7–66.5)		42.3 (35.3–49.7)	64.5 (56.6–72.7)***		39.0 (36.5–42.2)	66.3 (57.7–78.0)###

Data are presented as median (IQR). Mann-Whitney unpaired t-test was used to compare the differences between two groups. ^†, the unit is events/hour. **, P<0.01, ***, P<0.001 vs. untreated 30< AHI ≤50; ^##, P<0.01, ^###, P<0.001 vs. PAP-treated 30< AHI ≤50. AHI, apnea-hypopnea index; C90, percentage of SpO₂ <90% out of the total record time; IQR, interquartile range; LSpO₂, lowest oxygen saturation; ODI, oxygen desaturation index; OSA, obstructive sleep apnea; PAP, positive airway pressure; PSG, polysomnography; SpO₂, oxygen saturation; T90, percentage of SpO₂ <90% out of the total sleep time.

Sample collection, preparation, and storage

Ethylene diamine tetraacetic acid (EDTA)-anticoagulated peripheral blood (10 mL) was collected via venipuncture at five predefined time points: prior to, and at 1–2 weeks, 1 month, 3 months, and 6 months after administration of the third dose of the inactivated SARS-CoV-2 vaccines. Following collection, blood samples were centrifuged at 800 ×g for a duration of 10 min to separate the serum, and the cellular layer was further executed the density gradient centrifugation for PBMCs according to the instruction of operation (SepMate™-50, catalog number: #86460, STEMCELL). Serum aliquots were then stored at −80 ℃, while PBMCs were resuspended in cryopreserved solution [90% fetal bovine serum + 10% dimethyl sulfoxide (DMSO)] and stored at −80 ℃ with special cell cryopreservation box immediately overnight, subsequently transferred into liquid nitrogen for future analysis.

Detection of neutralizing antibody (nAb) with focus reduction neutralization test (FRNT)

Neutralization activity against SARS-CoV-2 was quantified using a FRNT, executed within a certified Biosafety Level 3 (BSL-3) facility. Briefly, 50 µL aliquots of plasma underwent serial dilution. Each diluted plasma sample was combined with an equal volume (50 µL) of ancestral SARS-CoV-2 virus suspension [containing approximately 100 focus-forming units (FFU)] in 96-well plates. This mixture was then maintained at 37 ℃ for 1 hour to facilitate neutralization. Following incubation, the plasma-virus mixtures were transferred onto confluent monolayers of Vero E6 cells [American Type Culture Collection (ATCC), Manassas, VA, USA] pre-seeded in 96-well plates. Adsorption was allowed to proceed for an additional hour at 37 ℃. Subsequently, the inoculum was aspirated, and an overlay medium [100 µL of minimal essential medium (MEM) supplemented with 1.2% carboxymethyl cellulose (CMC)] was added to each well. Plates were returned to the 37 ℃ incubator for a 24-hour period to permit viral replication and focus formation. After incubation, the overlay was carefully removed. Cells were then fixed in situ using a 4% paraformaldehyde solution for 30 min. Permeabilization was achieved with a 0.2% Triton X-100 solution. Immunostaining involved sequential incubations: first with a cross-reactive rabbit anti-SARS-CoV nucleocapsid (N) protein IgG antibody (Sino Biological, Inc., Beijing, China; catalog number: 40143-R001) for 1 hour at 37 ℃, followed by a horseradish peroxidase (HRP)-conjugated goat anti-rabbit IgG(H + L) secondary antibody (Jackson Immuno Research, West Grove, PA, USA; catalog number: 111-035-144; diluted 1:4000) at 37 ℃. Focus visualization was accomplished using KPL TrueBlue Peroxidase substrate (Seracare Life Sciences, Inc., Milford, MA, USA). The resulting SARS-CoV-2 foci were enumerated utilizing an Elispot reader (Cellular Technology Ltd., Shaker Heights, OH, USA).

The ancestral SARS-CoV-2 wildtype strain employed (SARS-CoV-2/human/CHN/IQTC01/2020; GenBank accession number: MT123290) was originally isolated from a COVID-19 patient and obtained from the Guangdong Provincial Centre for Disease Control and Prevention, China. All procedures involving authentic, infectious SARS-CoV-2 virus were conducted within the BSL-3 Laboratory at the Guangzhou Customs District Technology Center.

Detection of immune cellular response

Approximately three million cryopreserved PBMC were recovered, one million for antibody-secreting cells (ASCs) and circulating T follicular helper (cTfh) cells detection, and two million for specific CD4⁺ T and CD8⁺ T analysis through intracellular cytokine staining. Detailed experimental manipulation details are provided in Appendix 1. The antibodies involved in the study for were purchased from BD Biosciences (San Diego, CA, USA), BioLegend (San Diego, CA, USA), or Thermo Fisher Scientific (Waltham, MA, USA). The flow cytometric data were acquired on BD FACS Fortessa and analyzed with FlowJo software (BD Biosciences). Gating strategies are shown in Figure S1.

Statistical analysis

Sample sizes varied across different time points due to loss to follow-up, and not all samples were obtained from the same subjects. Statistical analyses were performed using GraphPad Prism software version 9.00. The Mann-Whitney unpaired t-test and the Chi-squared test were performed according to data types to compare the differences between groups. Spearman’s correlation was used to assess the relationship between different factors. A P value <0.05 (two-tailed) was considered statistically significant.

Results

Study cohort and vaccination information

To investigate the effects of OSA on immune responses following a third dose of inactivated SARS-CoV-2 vaccine, a total of 250 HDs and 300 patients with severe OSA (AHI >30 events/hour) were initially invited to participate in this study. Among them, 144 HDs and 193 OSA patients declined to enrollment. We finally included 213 participants in this study (106 HDs and 107 OSA patients). After excluding ineligible participants based on predefined criteria (Figure 1A), the cohort comprised 97 severe OSA participants (AHI >30 events/hour) and 88 HD (Figure 1A, Table 1). Participants in both groups received three doses of inactivated COVID-19 vaccines (CoronaVac or BBIBP-CorV) (Table 1). Follow-up visits were scheduled at five predefined time points: before vaccination, and 1–2 weeks, 1 month, 3 months, and 6 months post-third dose (Figure 1B). Blood samples were collected at each visit, though not all samples were available for every participant at each time point, with the number indicated in Figure 1B. Data on PAP for OSA participants were retrieved from machine records. No cases of breakthrough infection were reported within the cohort. Post-vaccination adverse events were documented via questionnaire, showing that local reactions primarily involved injection-site pain, while systemic reactions were primarily fatigue and myalgia. Statistical analysis indicated no significant differences in adverse reaction frequency or severity between the OSA and HD groups (Table 2).

Figure 1.

Cohort inclusion and sampling. (A) Flow chart of cohort inclusion. (B) Visiting time after the third boost inactivated vaccine injection. EDTA anticoagulated peripheral blood was collected for plasma and PBMC acquisition. Not all samples were available for every participant at each time point, and the number of samples at different stages were indicated below. EDTA, ethylene diamine tetraacetic acid; HD, healthy donor; NoSAS, neck circumference, obesity, snoring, age, sex; OSA, obstructive sleep apnea; PBMC, peripheral blood mononuclear cell.

A third booster vaccination improved the inferior SARS-CoV-2 specific humoral immunity in OSA participants

nAbs play a critical role in preventing viral entry, and their titers are key indicators of vaccine-induced protection. Utilizing a live virus neutralization assay, we assessed nAb levels against the ancestral SARS-CoV-2 strain in plasma samples from severe OSA participants and HDs following the third dose of the inactivated vaccine. nAb levels were quantified as the 50% focus reduction neutralization titer (FRNT50). Prior to receiving the third dose, approximately 6–7 months post-second dose, OSA participants exhibited a significantly lower geometric mean nAb titer [geometric mean titer (GMT): 10.29; 95% confidence interval (CI): 9.98–10.60] and a reduced positivity rate (4.1%) compared to HDs (GMT: 14.55; 95% CI: 13.02–16.25; positive rate: 58.8%) (Figure 2A), indicating weakened immune protection in severe OSA participants. However, after receiving the third dose of the inactivated vaccine, both the nAb titers and serum conversion rates in severe OSA participants significantly increased at multiple time points, reaching levels comparable to those of HDs (Figure 2B), highlighting the importance of booster vaccinations for individuals with severe OSA.

Figure 2.

SARS-CoV-2 specific antibody level before and after the booster immunization. Live virus nAb titer against ancestral SARS-CoV-2 in plasma of severe OSA participants (light purple) and HDs (grey) before (A) and after (B) booster vaccination. Serum conversion ratio and GMT were displayed above and cases number involved were marked below. Each dots indicates an individual case. nAb titer was shown as a geometric mean with 95% CI. Unpaired and nonparametric Mann-Whitney test was performed between two groups. ****, P<0.001, two tailed; ns, not significant. CI, confidence interval; FRNT50, 50% focus reduction neutralization titer; GMT, geometric mean titer; HD, healthy donor; LOD, limit of detection; nAb, neutralizing antibody; OSA, obstructive sleep apnea; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

Severity-dependent impairment of immune recall in untreated OSA participants post-booster

To determine whether the severity of OSA influences vaccine-induced immune response levels, we analyzed this relationship in untreated OSA participants (Table 3). Our study revealed significant negative correlations between nAb titers 1 month post-third vaccine dose and these clinical indices: AHI (ρ=−0.453, P=0.006), ODI (ρ=−0.464, P=0.005), T90 (ρ=−0.403, P=0.02), and C90 (ρ=−0.448, P=0.008). A trend toward positive correlation with LSpO₂ was also noted (ρ=0.280, P=0.10) in untreated OSA participants (Figure 3A). Notably, no significant correlation was observed between nAb titers and body mass index (BMI) (ρ=−0.051, P=0.77), suggesting that factors beyond obesity influence immune responses in these participants.

Figure 3.

Correlation of OSA severity indices and peak Immune responses post booster vaccination in untreated OSA participants. (A) Presentation of the correlativity between nAb titer and different clinical index scores in severe UT-OSA participants at 1 month post boost vaccine. (B) Correlation matrix overview of clinical indices of UT-OSA participants and corresponding humoral and cellular immunological parameters at 1 month post vaccination. Clinical disease severity indices were exported from the full-night PSG before the first sampling. UT-OSA, OSA participants without any symptomatic treatment before and during our follow-up period, n=35. Gating strategies for cellular responses were detailed in Figure S1. Each dot indicates an individual case. Nonparametric Spearman’s correlation was performed. *, P<0.05; **, P<0.01, two tailed. AHI, apnea-hypopnea index; ASC, antibody-secreting cell; BMI, body mass index; C90, percentage of SpO₂ <90% out of the total record time; cTfh, circulating T follicular helper; LSpO₂, lowest oxygen saturation; nAb, neutralizing antibody; ODI, oxygen desaturation index; OSA, obstructive sleep apnea; PSG, polysomnography; SpO₂, oxygen saturation; T90, percentage of SpO₂ <90% out of the total sleep time; Tcm, central memory T; Tem, effector memory T; Temra, effector memory T express CD45RA; Tnaive, naïve T.

T follicular helper (Tfh) cells are essential for humoral immunity, facilitating B cell activation, class-switching, and antibody production. To further evaluate the immune response, we assessed ASCs, cTfh cells, and antigen-specific T cell populations post-booster, with gating strategies illustrated in Figure S1A. Spearman correlation analysis indicated negative correlations of ASC with AHI (ρ=−0.536, P=0.042), ODI (ρ=−0.682, P=0.006), C90 (ρ=−0.543, P=0.04), and T90 (ρ=−0.604, P=0.02), consistent with the nAb data (Figure 3B). Frequencies of cTfh and functional CD40L⁺ cTfh cells exhibited negative correlations with OSA severity indices, with cTfh showing statistical significance to BMI (ρ=−0.555, P=0.007) while CD40L⁺ cTfh to AHI (ρ=−0.616, P=0.02) and ODI (ρ=−0.523, P=0.048) (Figure 3B). Although no significant correlation was found in IFN-γ-expressing antigen-specific CD8⁺ T cells, the frequency of IFN-γ-expressing antigen-specific CD4⁺ T cells demonstrate negative correlations with OSA severity, particularly with ODI (ρ=−0.441, P=0.04) and LSpO₂ (ρ=0.518, P=0.01). Moreover, memory populations of specific CD4⁺ T cells were also affected, with central memory T (Tcm) negatively correlating with C90 (ρ=−0.518, P=0.01) and T90 (ρ=−0.533, P=0.01), and effector memory T express CD45RA (Temra) positively correlating with indices like C90 (ρ=0.436, P=0.04) and T90 (ρ=0.412, P=0.06), while also negatively correlating with LSpO₂ (ρ=−0.587, P=0.004) (Figure 3B). These findings suggest that increased OSA severity impairs immune recall post-vaccination.

Impaired immune recall in untreated OSA participants with AHI >50 events/hour

Given the observed negative impact of OSA on immune responses, we further stratified untreated participants that with nAb titer and cellular response data available at 1 month post booster vaccination (n=37) based on the median AHI (50.1 events/hour): those with an AHI =30–50 events/hour (range, 30.1–49.3, median: 38.9; n=18) and those with an AHI >50 events/hour (range, 50.1–82.0; median: 63.1; n=19). In the case of similar nAb titers and cellular response levels before booster immunization (Figure S2), participants with AHI >50 events/hour showed significantly reduced nAb titers 1-month post-booster compared to HDs (P=0.007) (Figure 4A). Additionally, this group displayed lower frequencies of ASC (P=0.04), total cTfh (P=0.053), and CD40L⁺ cTfh (P=0.18) compared to HDs (Figure 4B-4D), and showed reduced frequencies of specific CD4⁺ and CD8⁺ T cells (Figure 4E,4F), though these differences did not all reach statistical significance. Additionally, lower detectable rates of specific T cells were noted (HD vs. AHI =30–50 vs. AHI >50 events/hour: specific CD4⁺ T: 91% vs. 90% vs. 75%; specific CD8⁺ T: 77% vs. 70% vs. 58%), along with a lower proportion of effector memory T (Tem) among specific CD4⁺ (P=0.04) and CD8⁺ T cells (P=0.10) (Figure 4G,4H). Overall, OSA participants with AHI =30–50 events/hour showed less impairment in immune responses compared to those with AHI >50 events/hour (Figure 4), highlighting the severity-dependent impact of OSA on immune response following booster vaccination.

Figure 4.

Immune responses at the peak responsive stage post booster vaccination in untreated OSA participants with two severity degree. Untreated severe OSA participants that with nAb titer or cellular responses data available at 1 month post booster vaccination (n=37) were divided into two subgroups based on the median AHI (50.1 events/hour): those with an AHI =30–50 events/hour (range, 30.1–49.3; median: 38.9) and those with an AHI >50 events/hour (range, 50.1–82.0; median: 63.1). (A) nAb titer against ancestral SARS-CoV-2. The GMT was displayed above. (B,C) Frequency of ASCs (B) and frequency of cTfh (C). Gating strategy related to (B,C) was detailed in Figure S1A. (D-F) Frequency of CD40L⁺ cTfh, IFN-γ-secreting CD4⁺ T (specific CD4⁺ T), and IFN-γ-secreting CD8⁺ T (specific CD8⁺ T), frequency with control subtraction, and the percentage of positive-detected specific T (pep-ctrl >0) were annotated on the top of statistical chart. (G,H) Memory differentiation subset consists of Tnaive (CD45RA⁺CCR7⁺), Tcm (CD45RA⁻CCR7⁺), Tem (CD45RA⁻CCR7⁻), Temra (CD45RA⁺CCR7⁻) of specific CD4⁺ T and specific CD8⁺ T after peptides stimulating, and asterisk (*) colors were consistent with figure legends on the right. Gating strategy related to (D-H) was detailed in Figure S1B. HD: healthy donor, n=68; UT-O, 30–50: untreated OSA participants with AHI score among 30 to 50 events/hour, n=18; UT-O, >50: untreated OSA participants with AHI score higher than 50 events/hour, n=17. Not every individual’s nAb titer or cellular response data at each timepoint were available (blood unavailable), and each data point represents an individual case. nAb titer was showed as a geometric mean with 95% CI, and cellular response data were shown as a mean with SEM. Unpaired and nonparametric Mann-Whitney test was performed between the two groups. *, P<0.05; **, P<0.01, two tailed, ns, not significant. AHI, apnea-hypopnea index; ASC, antibody-secreting cell; CI, confidence interval; cTfh, circulating T follicular helper; FRNT50, 50% focus reduction neutralization titer; GMT, geometric mean titer; nAb, neutralizing antibody; OSA, obstructive sleep apnea; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; SEM, standard error of the mean; Tcm, central memory T; Tem, effector memory T; Temra, effector memory T express CD45RA; Tnaive, naïve T.

PAP treatment potentially enhanced humoral immunity in OSA participants

The role of PAP in improving immune responses post vaccination among OSA participants remains unclear. In our study, OSA participants with who had started PAP treating prior to their third vaccination were classified as the treated OSA group [Table 3, median days of PAP treatment to third vaccination: 305 (range, 54–981)]. Analysis revealed that PAP-treated OSA participants with AHI >50 events/hour exhibited higher nAb titers both before and after the third dose vaccination, particularly at the peak (1 month) response stage (P=0.003), compared to untreated OSA participants (Figure 5A). There was no obvious difference between less severe (AHI =30–50 events/hour) OSA participants with PAP-treated and those without treatment (Figure S3). No significant discrepancies were observed between treated and untreated participants in terms of ASC, total cTfh, and CD40L⁺ cTfh frequencies (Figure 5B). These results suggest that PAP treatment may enhance antibody responses in OSA participants, potentially improving their resistance to SARS-CoV-2 infection.

Figure 5.

Immune responses in severe OSA participants with AHI >50 events/hour after PAP treatment. Severe OSA participants who start PAP treating prior to their third vaccination were classified as the treated OSA group. (A) Live virus nAb titer against ancestral SARS-CoV-2 at different stages post booster vaccination. Serum conversion ratio and GMT were displayed above and cases number involved were marked below. (B) Frequency of ASC, cTfh, and CD40L⁺ cTfh at 1 month post booster vaccination. UT-OSA, OSA participants without any symptomatic treatment before and during our follow-up period (blue); T-OSA, OSA participants who start PAP treatment before their third vaccination (green). Not every individual’s nAb titer or cellular response data at each timepoint were available (blood unavailable), and each data point represents an individual case. nAb titer was showed as a geometric mean with 95% CI, and other data were shown as a mean with SEM. Unpaired and nonparametric Mann-Whitney test was performed between two groups at the same. **, P<0.01, two tailed, ns, not significant. AHI, apnea-hypopnea index; ASC, antibody-secreting cell; CI, confidence interval; cTfh, circulating T follicular helper; FRNT50, 50% focus reduction neutralization titer; GMT, geometric mean titer; nAb, neutralizing antibody; OSA, obstructive sleep apnea; PAP, positive airway pressure; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; SEM, standard error of the mean.

Discussion

The high prevalence of OSA has garnered attention in public health and sleep medicine. Circadian rhythms and sleep quality critically influence immune function, with sleep deprivation recognized as a risk factor for diminished vaccine responses (15,33-35). Given the concurrent rise in OSA burden and COVID-19 vaccination, our study aimed to evaluate the effects of OSA on immune responses following booster vaccination against COVID-19.

The reduced nAb titers observed in OSA participants post-booster suggest a heightened susceptibility to SARS-CoV-2 infection. Notably, the third dose of the inactivated vaccine improved immune responses to levels comparable to HDs, without significant adverse effects, underscoring the critical need for booster vaccinations in severe OSA cases.

Furthermore, our findings also reveal that the severity of OSA impacts immune recall, affecting both humoral and cellular immunity, as well as the differentiation of specific memory T cells. Untreated OSA participants with an AHI >50 events/hour exhibited significant declines in nAb titers, ASC frequencies, and cTfh frequencies. This aligns with previous studies showing that sleep deprivation and shortened sleep duration can weaken immune responses to vaccines, such as those for influenza (36,37) and hepatitis (38). Importantly, concurrent PAP treatment during vaccination appears to enhance humoral immunity in OSA participants, suggesting a potential strategy to mitigate the immunosuppressive effects of OSA and improve vaccine efficacy.

The impaired vaccine immune response in the untreated OSA group was improved after PAP treatment. The potential explanations could be related to the improvement of immune status after PAP treatment. Both physiological disorders of OSA, including chronic IH and SF, are linked to chronic immune dysregulation in OSA patients, influencing the number and function of various immune cells, including T cells, B cells, monocytes, as well as dendritic cells (DCs) (39-43). Hypoxia is closely associated with factors like hypoxia-inducible factor-1 (HIF-1α) and the NLRP3 inflammasome (44,45). This interaction leads to elevated plasma levels of inflammatory markers such as IL-6 and IL-8 (11,46), developing a low-grade systemic inflammation and a compromised immune response. Disturbances in circadian rhythms can influence hormone secretion via the key regulator BMAL1, thereby diminishing the migration of DCs to the draining lymph nodes (46), and adversely impacting the antigen-presenting function of DCs (33). Consequently, this restricts interactions with T cells and hinders lymphocyte infiltration and lymph node expansion, as well as the formation of adaptive immune memory, all of which are essential for an effective response to immunization. However, PAP treatment helps to mitigating the impact of chronic IH and SF on the immune system in OSA participants, reducing the expression of PD-L1 on the surface of monocyte and T cells, and restore the composition and function of immune cells, including monocyte, DC, B, and T cells (28-30,47).

In contrast, a study by Tufik et al. (26) reported no significant correlation between OSA severity and reduced anti-SARS-CoV-2 IgG levels in older participants after receiving COVID-19 vaccine, although a trend towards lower serum IgG levels was noted in the severe OSA group. This discrepancy may arise from differences in sample selection criteria and the immunological endpoints of interest. In this study, we observed a negative correlation between immune recall and disease severity in severe OSA participants, with uniform sampling at the peak response stage after the third booster, specifically involving inactivated COVID-19 vaccine recipients. While Tufik et al. assessed varied sampling stages following primary vaccination with different vaccine types [inactivated, messenger RNA (mRNA), and adenovirus vector] across a broader spectrum of OSA severity on elderly participants. Consistent with this, participants with milder OSA exhibited a lesser impact on immune recall following booster vaccination in this study.

There are several limitations to our study. Firstly, the lack of pre-vaccination samples and post-second dose data restrict our ability to assess baseline immune status and compare responses among treated and untreated OSA participants as well as HDs. Secondly, while we noted a pronounced impact of OSA on immune recall in severe cases, the limited sample size of untreated OSA participants hinders our ability to identify a specific clinical score threshold that predicts significant declines in humoral immune response. Lastly, the absence of AHI scores from full-night PSG post-PAP treatment limits our capacity to assess the impact of PAP on vaccination outcomes relative to OSA disease severity.

Conclusions

Our findings reveal an inverse correlation between OSA severity and immune response in untreated participants, with those exhibiting an AHI >50 events/hour showing notably reduced nAb titers, ASC frequencies, and cTfh cells, indicating an impaired immune recall response. By contrast, PAP-treated participants demonstrated enhanced humoral immunity, particularly at peak response stages.

The findings indicate that the immune response to COVID-19 vaccination in individuals with OSA is influenced by both the severity of the disease and the use of PAP therapy, highlighting the potential role of PAP treatment in enhancing vaccine efficacy. Given the high prevalence of OSA and its association with increased risk of severe COVID-19 outcomes, our valuable clinical samples and research data provide important insights into the immune responses of OSA patients following a third dose of an inactivated SARS-CoV-2 vaccine. These results help address the existing gap in knowledge regarding vaccine-induced immunity within this population. Our study underscores the importance of considering both disease severity and therapeutic intervention when developing vaccination strategies for individuals with OSA. For patients with more severe forms of OSA, the proactive implementation of PAP therapy may be critical to maximizing the immunoprotective effects of vaccination—not only for COVID-19, but potentially for other vaccines as well.

Supplementary

The article’s supplementary files as

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Medical Ethics Committee of the First Affiliated Hospital of Guangzhou Medical University (No 2021-78) and informed consent was obtained from all individual participants.

Data Sharing Statement

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DOI: 10.21037/jtd-2025-391