The Humoral Response of Patients With Cancer to Breakthrough COVID-19 Infection or the Fourth BNT162b2 Vaccine Dose

Abstract

Since January 2022 in Israel, high-risk populations with underlying health conditions were advised to receive a fourth dose of the BNT162b2 vaccine (Pfizer-BioNTech) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We monitored vaccine-induced immunity among oncology patients undergoing systemic anti-cancer therapy before and after the 4th-BNT162b2-dose. Three groups of patients were included in the study: those who received 3rd-BNT162b2-dose and had no breakthrough infection (control), those who received 3rd-BNT162b2-dose and had the breakthrough infection, and those who received the 4th-BNT162b2-dose and had no breakthrough infection. Anti-SARS-CoV-2 immunoglobulin-G (IgG) levels of the control group exhibited a rapid decrease over time, whereas IgG titers of patients with breakthrough-infections or patients vaccinated with the 4th-BNT162b2-dose were considerably elevated, consistent with the capacity of the second booster to induce anti-SARS-CoV-2 IgG levels. Additionally, oncology patients’ humoral immune response was significantly greater after breakthrough-infection than in response to the 4th dose of BNT162b2.

Since January 2022 in Israel, high-risk populations with underlying health conditions were advised to receive a fourth dose of the BNT162b2 vaccine against SARS-CoV-2. This article reports on vaccine-induced immunity among oncology patients undergoing systemic anti-cancer therapy before and after the 4th-BNT162b2-dose.

Introduction

On January 2, 2022, the Israeli Ministry of Health recommended that high-risk individuals, such as oncology patients, be vaccinated with a 4th dose of the BNT162b2 vaccine (4th-BNT162b2-dose) (BioNTech Pfizer) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). With the emergence of new SARS-CoV-2 variants, evidence of reduced antibody neutralizing activity against Omicron, and fading antibody levels after the 3rd dose of BNT162b2 (3rd-BNT162b2-dose), vaccine-breakthrough became a significant hazard. Along with the lack of clinical data on the effectiveness of multiple vaccine boosters and their potential adverse impact on the immune response to COVID-19 (leading, eg, to T-cell exhaustion), our current study aimed to provide data on multiple anti-Covid-19 boosters by assessing the efficacy of the 4th-BNT162b2-vaccine dose in oncology patients.¹ To achieve this, we performed a follow-up study in a small cohort of oncology patients recently included in a study monitoring anti-SARS-CoV-2 immunoglobulin-G (IgG) levels after the 3rd-BNT162b2-dose.²

Materials and Methods

Participants and Design

All study participants were oncology patients with solid tumors undergoing anti-cancer therapy (Supplementary Table S1) at the oncology unit, Emek Medical Center. Inclusion criteria: 18 years and above, previously included in our recent study (n = 154) monitoring vaccine-derived immunity to the 3rd-BNT162b2-dose (BioNTech Pfizer, NY, US)² and having signed a consent form regarding participation in the current follow-up experiment. At study initiation, exclusion criteria were previously confirmed records of COVID-19 infection (before the 2nd BNT162b2 dose) and active autoimmune disease. The current study cohort (n = 42) included 21 males and 21 females aged 63-68 (Supplementary Table S1). Blood samples were collected up to 30 days before the patient’s scheduled 4th-BNT162b2-dose. A second blood sample was collected 30-90 days after either a breakthrough-infection (median of 166.00 days from dose 3; interquartile range (IQR) [139.00, 173.00]) or the administration of the 4th-BNT162b2-dose (median of 166.00 days from dose 3; IQR[161.00, 177.50]). To adjust and match the follow-up IgG sampling times of a control group of patients vaccinated with the 3rd-BNT162b2-dose but not with the 4th-BNT162b2-dose and with no breakthrough-infection to those of the other study groups, we scheduled IgG blood tests for all control group participants 160 days after the 3rd-BNT162b2-dose (median of 160 days; IQR[148.25, 170.50]) (Supplementary Table S2). Data were collected as follows: (i) patients reporting Covid-19 infection between the collection of the 2 blood samples (breakthrough-infection group, n = 9), (ii) patients administered the 4th-BNT162b2-dose between the 2 blood samples which did not experience breakthrough-infection (4th-BNT162b2-dose group, n = 11), and (iii) patients electing not to receive the 4th-BNT162b2-dose who did not experience Covid-19 breakthrough-infection (control group, n = 22).

Immunoassay

Anti-SARS-CoV-2 IgG titers were quantified using the SARS-CoV-2 IgG serological immunoassay (Alinity, Abbott Core Laboratory, IL, US).² As per the manufacturer’s protocol and the limitations of this assay, minimum values for seropositive detection were set at 50 arbitrary units per milliliter (AU/mL), and maximum detection values were set at 40 000 AU/mL.²

Statistical Analysis

To compare results among the groups, we used The Wilcoxon rank U test, equivalent to the Mann-Whitney U test for the 2 small groups used in the study. For post hoc testing (Fig. 1b), we used a one-sample t-test to determine whether the IgG titers measured during the second blood test differed significantly from the constant IgG titers (40 000 AU/mL) of the breakthrough-infection group. The threshold of statistical significance was set at 0.05.

Figure 1.

Analysis of specific anti-SARS-CoV-2 IgG levels in fully vaccinated (third BNT162b2 dose) oncology patients as compared to patients receiving a 4th BNT162b2 dose or experiencing a breakthrough infection. (A) Quantification of IgG levels against the spike receptor-binding domain (RBD) of SARS-CoV-2 in patients vaccinated only with the 3rd-BNT162b2 dose (Control; n = 22), patients vaccinated with the second BNT162b2 booster (4th-BNT162b2 dose; n = 11), or patients who experienced Covid-19 breakthrough infections (breakthrough infection; n = 9). Blood test indicates IgG levels at baseline (after the 3rd-BNT162b2 dose), and blood test-2 indicates IgG levels after breakthrough infection, the 4th-BNT162b2-dose or matched or a corresponding time range for the Control group. (B) Comparison of levels of anti-SARS-CoV-2 IgG measured during the second blood test (blood test-2) is presented as the median and interquartile range (IQR) (see also Supplementary Table S1). Significant differences (P < .05) are indicated using horizontal solid lines.

Results

To assess the humoral responses in oncology patients undergoing anti-cancer therapy to the 4th-BNT162b2-dose vaccine dose, we compared anti-Covid-19 IgG levels in a cohort of 42 patients before and after vaccination (4th-BNT162b2-dose group, n = 11), a confirmed breakthrough-infection (breakthrough-infection group, n = 9) or in a control group of patients only vaccinated with the 3rd-BNT162b2-dose (Control group, n = 22). Covid-19 breakthrough-infections after the 3rd-BNT162b2-dose occurred on an average of 136.6 days after the 3rd-BNT162b2-dose when the 4th-BNT162b2-dose was administrated on an average of 131 days after the 3rd-BNT162b2-dose.

Around 63-68 days after the 3rd-BNT162b2-dose, we quantified IgG levels against the spike RBD of SARS-CoV-2 by serological immunoassay for all study participants (IgG blood-test-1). A second blood sample (IgG blood-test-2) was collected 30-90 days post-breakthrough-infection or administration of the 4th-BNT162b2-dose. The anti-SARS-CoV-2 IgG titers of the control group were analyzed 160-166 days after the 3rd-BNT162b2-dose to blood-test-2 (P = .169) (Supplementary Table S2).

Results showed no significant difference between the groups in levels of anti-SARS-CoV-2 IgG titers at baseline (blood-test-1) (Fig. 1a and Supplementary Table S2; IgG blood-test-1; P = .647). Levels of anti-SARS-CoV-2 IgG in the control group dropped sharply from 5379.95 AU/mL (IQR [2030.95, 25 999.52]) at blood-test-1 to 2314.00 AU/mL (IQR [459.00, 5540.05]) at blood-test-2 (P < .001) (Fig. 1a), consistent with the reports of the waning Covid-19 immunity.³ Patients in the breakthrough-infection group showed a large and significant increase in anti-SARS-CoV-2 IgG titers from 7050.50 AU/mL (IQR [3329.50, 11 514.50]) to 40 000.00 AU/mL (IQR [39 873.00, 40 000.00])(P < .001) (Fig. 1a). Comparing anti-SARS-CoV-2 IgG titers after breakthrough-infection to control at blood-test-2 also showed a large and significant difference (40 000.00 AU/mL to 2314.00 AU/mL, P < .001) (Fig. 1b).

Patients in the 4th-BNT162b2-dose group also exhibited a fairly significant increase in anti-SARS-CoV-2 IgG titers at blood-test-2, increasing from 8389.00 AU/mL (IQR[5154.85, 27962.80]) to 22 914.00 AU/mL (IQR [16 562.00, 40 000.00] (P = .033) (Fig. 1a) and compared with the control group (P < .001) (Fig. 1b), highlighting the capacity of the 4th-BNT162b2-dose to boost anti-SARS-CoV-2 IgG levels among patients with cancer.^4,5

Notably, when comparing patients vaccinated with the 4th-BNT162b2-dose to those who experienced breakthrough-infections, anti-SARS-CoV-2 IgG levels in the breakthrough-infections group (40 000.00 AU/mL; IQR [39 873.00, 40 000.00]) were significantly higher than those of the 4th-BNT162b2-dose group (22 914.00 AU/mL; IQR [16 562.00, 40 000.00]) (P = .005) (Fig. 1b).

Discussion

Though the number of participants in this study was small, caution should be taken with inferences and generalizations based on these results; our data nonetheless indicated that oncology patients, who were at a higher risk of Covid-19 infection with more severe outcomes,¹ achieved more robust humoral immune responses following Covid-19 breakthrough-infection after receiving their 3rd^-BNT162b2-dose than those vaccinated with 4th-BNT162b2-dose who had no breakthrough-infection. These findings are consistent with recent observations in healthy individuals undergoing repeated SARS-CoV-2-S hybrid exposure.⁶ At the comparative timepoint used in this study, anti-SARS-CoV-2 IgG levels in oncology patients who had only received the 3rd-BNT162b2-dose were significantly lower than those who received the 4th-BNT162b2-dose. Thus, immunity against Covid-19 rapidly wanes in patients who did not experience any exposure to SARS-CoV-2 spike-proteins either through infection or by administration of additional boosters.

In line with our results, recent evidence indicates that Covid-19 breakthrough-infections can better protect against hospitalization, effectively preventing reinfection and improving survival irrespective of Covid-19 variant,⁷ eliciting potent, durable, and broad neutralizing antibody responses.^6,7 As future Covid-19 variants emerge⁸ and the duration of 4th-BNT162b2-dose protection remain unknown, and in light of the lack of reports showing that multiple vaccine boosters improved protection against infection,⁹ we suggest oncology patient infection history should be considered when evaluating the risks and outcomes associated with the new booster regimen considering risk magnitude conferred by a new infection. It is essential to balance these risks against the apparently small but existent risks of harm of repeated vaccination and the cost-benefit of the different options.¹⁰

Further studies of BNT162b2-boosters in cancer patients should be compared to the general population assessing whether recurrent boosters or breakthrough-infection affords better immune durability and may prevent the need for routine vaccine boosters.⁹

Funding

Research in our laboratory is funded by the Ministry of Health (Jerusalem, Israel), grant number 3000015198, and the Israeli Cancer Association, grant number 2020002.

Ethical Statement

All study participants signed an informed consent form included in the study protocol, which had been authorized and approved by the Institutional Ethics Committee (0133-21-EMC). The study was designed and conducted according to the guidelines and rules of the Helsinki declaration for human medical experiments ethical code.

Conflict of Interest

The authors indicated no financial relationships.

Author Contributions

Conception/design: I.C., G.B.S. Provision of study material or patients: C.R., O.R., G.B.S. Collection and/or assembly of data: O.R., R.C. Data analysis and interpretation: I.C., S.C.P., G.B.S. Manuscript writing: I.C., S.C.P., G.B.S. Final approval of manuscript: All authors.

Data Availability

The data used and analyzed in the study is available from the corresponding authors upon request.