Challenging 21-day quarantine guidelines for mumps in Beijing: Data-driven recommendations for a high-coverage MMR vaccination era (2019–2024)

ABSTRACT

Mumps is a vaccine-preventable disease. Following Beijing’s implementation of a three-dose MMR vaccination strategy, incidence rates declined significantly. However, the current 21-d quarantine period lacks evidence-based support, resulting in low compliance and conflicts between healthcare providers and patients. This study analyzed 2019–2024 surveillance data to characterize mumps in the vaccine era through viral shedding detection. Study participants were NNDRS-reported mumps cases with both registered and collective residences in Beijing’s Chaoyang District, who signed informed consent for shortened isolation surveillance. Data were integrated from three sources: 1) National Notifiable Disease Reporting System cases; 2) Beijing’s immunization registry; and 3) epidemiological/laboratory records. PCR and/or serology-confirmed cases (Chaoyang CDC) were analyzed for demographics, clinical features, and vaccination history. Quarantine clearance was based on test results. From 2005 to 2024, 8,070 mumps cases were reported in Chaoyang District (average annual incidence: 12.69/100,000), showing a downward trend. Among 146 cases (2019–2024), 95.89% were childcare/school attendees; 141 received ≥1 MMR dose. All cases presented parotid swelling (duration: 1–12 d, 97.26% ≤9 d), with no complications. Of the 526 samples, 4 tested PCR-positive, 6 IgM-positive, and 18 IgG-confirmed. Quarantine was safely reduced from 21 to 9 d in 88.36% (129/146) of cases without increasing outbreak risks. The 21-d quarantine standard is outdated due to evolving epidemiological patterns. Recommendations include adopting molecular diagnostic criteria, validating a ≤5-d quarantine via multicenter studies, and establishing dynamic vaccine efficacy monitoring for targeted prevention.

Introduction

Mumps is an acute respiratory infectious disease caused by the rubulavirus, which belongs to the Paramyxoviridae family (referred to as mumps virus, MuV),¹ mainly transmitted via droplets, and predominantly affecting children and adolescents. It is worth noting that mumps in adolescents may be accompanied by orchitis, which can potentially lead to fertility issues.¹ In China, it is a notifiable Class C infectious disease, with mandatory reporting within 24 h through the National Notifiable Disease Reporting System (NNDRS) since 2004. As a vaccine-preventable disease, vaccination with mumps-containing vaccine (MuCV) is the most effective control measure, with 124 countries worldwide including it in their immunization programs by 2023.²

China incorporated MuCV into its National Immunization Program (NIP) in 2008, offering a dose to children aged 18–24 months.³ In 2020, the national schedule was adjusted to two dose of measles-mumps-rubella combined attenuated vaccine (MMR) at 8 and 18 months.⁴ Beijing, a pioneer in mumps vaccination, has implemented a three-dose MMR schedule (at 8 months, 18 months, and 6 y) since 2020-one of only three cities in China to do so, the other two cities are Shanghai and Tianjin.⁴ Children may be vaccinated only when reaching the age specified in the immunization schedule. It is recommended to complete it within the month, with no advance shots and no excessive delay. Those under 18 y old who missed a dose can get the supplementary vaccination as required.

Studies have shown that the first dose of MMR vaccine administered at 8 months of age demonstrates satisfactory immunogenicity, effectiveness, and safety.^5,6 As a national immunization program vaccine, the MMR vaccine is free and mandatory for children. It is mainly provided by the preventive health care departments of community health service centers in each sub-district (township). Children’s vaccination certificates are checked when they enter kindergartens or schools to ensure age-appropriate children complete vaccination as required. The study population received only one type of vaccine, specifically the MMR vaccine produced by China National Biotec Group (CNBG). Vaccine has significantly reduced incidence: China’s annual reported rate declined from 35.59/100,000 in 2012 to 6.47/100,000 in 2023,⁷ and in high-coverage areas like Beijing, most clinically reported cases have immunization history. The vaccine does not fully prevent disease onset but typically results in milder symptoms – often transient, with parotid pain lasting just 1–2 d and no other symptoms.

Current isolation guidelines for mumps in China lack uniformity. Beijing’s 2018 surveillance protocol mandates 21-d isolation post-onset,⁸ but this faces low compliance: patients (mainly students) and parents often dispute the prolonged period, as symptoms resolve long before isolation ends, leading to school absences and complaints. Meanwhile, whether the 21-d isolation period is suitable for the current case characteristics, but there is a lack of relevant evidence-based medical evidence to modify the isolation period. Other regions recommend isolation until parotid swelling subsides (e.g., Shanghai, Guangzhou),^9–12 while Hunan’s guidelines – either 9 d or until swelling resolves – date back to 2005 or 2016, with no national updates.^13,14

In the absence of uniform and authoritative guidelines at the national level, it is difficult to assess the effectiveness and reasonableness of isolation policies in different regions. Therefore, the Beijing Municipality has taken Chaoyang District as a pilot area to carry out the relevant research from 2019, named as the Isolation Surveillance Pilot Project, hoping that through long-term monitoring data analysis, it can provide a basis for the development of scientific and reasonable isolation measures for the high immunity coverage population.

Material and methods

Research site

Chaoyang District is one of the six urban districts of Beijing, located in the south-central part of the city, with an area of 470.8 km² and a flat topography. As the largest of Beijing’s suburban districts, Chaoyang District has a resident population of 3.45 million according the 2020 Seventh Population Census. Chaoyang District is one of Beijing’s financial, commercial and international trade centers, as well as an important area for foreign affairs activities. Chaoyang District has the largest number of primary and secondary schools in Beijing and also has the highest number of reported cases of mumps in Beijing.

Data sources

Case data came from the NNDRS. Vaccine immunization history was obtained from the Beijing Vaccination Information System, and those whose information records could not be located were judged to have an unknown immunization history. The surveillance program requires epidemiological investigation and sample collection for each reported mumps case, and entry of relevant information into the Chaoyang Digital Epidemiological Survey System (CYDES) to form a database. For each case, the CYDES database routinely captured age, sex, occupation, vaccination history (number of MMR doses and dates, or “unknown” if records were missing), clinical symptoms (parotid swelling, fever, orchitis, etc.), and laboratory test results (IgM/IgG serology and/or RT-PCR for mumps virus), and other relevant information (e.g., contact history, date of onset, hospitalization status, etc.).

Case definition

According to the diagnostic criteria of the Chinese Ministry of Health, a clinically diagnosed case of mumps is defined as an acute onset of unilateral or bilateral swelling of the parotid and/or other salivary glands characterized by any of the following, which cannot be explained by other diseases: (1) fever, headache, weakness, and loss of appetite; (2) orchitis; (3) pancreatitis; and (4) encephalitis and/or aseptic meningitis. Laboratory diagnosed cases are clinically diagnosed cases meeting one of the following conditions: (1) the patient has not received MuCV within 1 month, and the serum is positive for specific IgM antibody; (2) double serum (2–4 weeks apart) with fourfold or more increase in IgG antibody titre (including positive antibody transfer); (3) isolation of mumps virus in saliva, urine, cerebrospinal fluid and other body fluids.¹⁵ Since the Polymerase Chain Reaction (PCR) technology was invented in the 1980s, it has been widely applied in the diagnosis of infectious diseases. Owing to its rapidity, sensitivity, quantification, and reliability, PCR testing has been extensively adopted in Beijing. Therefore, in this article, we classify PCR-positive cases as laboratory diagnostic cases as well. In Beijing, a mumps outbreak is defined as the occurrence of ≥5 mumps cases in a community, school, company or other setting within 14 d. Mumps clustered outbreak refers to an occurrence of three or four mumps cases within 14 d in a collective unit (such as a childcare center, school, or workplace).¹⁶

Inclusion and exclusion criteria

Inclusion Criteria:

(1) Mumps cases reported through NNDRS that met the clinical diagnosis or laboratory-confirmed criteria as specified in 2.4 Case definition; (2) Cases whose current address and collective unit were both located in Chaoyang District, Beijing, and who had signed the paper “Informed Consent for Monitoring of Shortened Isolation Period for Mumps in Chaoyang District,” which detailed the specific sampling procedures for patients (including the multiple parotid duct swab collections that might be involved for PCR testing) as well as the conditions for lifting isolation and other relevant information; (3) Cases with the most authoritative diagnosis retained after duplicate checking in accordance with the statutory infectious disease reporting and review regulations; (4) Cases of reinfection after recovery confirmed by epidemiological investigation information on CYDES, as well as cases of “re-infection” or recurrent cases related to immunocompromise (no such cases had been found so far).

Exclusion Criteria:

(1) Cases that did not agree to participate in this study; (2) Cases whose current address and collective unit were both not located in Chaoyang District, Beijing; (3) Cases with non-authoritative diagnoses that were cleared after duplicate checking in accordance with the statutory infectious disease reporting and review regulations.

Note: Mumps was generally considered to confer lifelong immunity, and in practice, no cases of reinfection or immunocompromise-related recurrent cases had been found so far.

Specimen collection method

Bilateral parotid duct swabs, referred to as PDS, were collected from each patient, whether unilaterally or bilaterally enlarged, on both sides. Before collection, the cheek corresponding to the mouth of the parotid duct or the lower part of the swelling in front of the ear was gently pressed with the hand to promote salivary outflow. The collection site was the buccal mucosa opposite the buccal surface of the maxillary second molar crown. One sterile cotton swab was placed at the mouth of the parotid duct on each side, and the two swabs were placed together into a virus sampling tube containing the specimen preservation solution after aspirating a full amount of saliva (approximately 30 s). The specimens were stored at 2°C～8°C and transported to the laboratory for PCR identification of mumps virus within 24 h.

Specimen collection time and isolation time

The patient’s first PDS was collected within 48 h after the case being reported in the CDPCIS. Subsequently, the patient’s second PDS, third PDS, and subsequent samples were collected at 2-d intervals. The case can be released from quarantine only after two consecutively negative PDS results are obtained.

Study design and sample size estimation

Study participants were mumps cases reported in NNDRS whose registered address and collective residence were both in Beijing’s Chaoyang District and who had signed the informed consent for the shortened-mumps-isolation surveillance. These participants underwent sample collection, testing, and isolation release following the procedures described in sections 2.4 and 2.5 from 2019 to 2024. The minimum sample size was estimated using a random-sampling formula: N =$\mathit{\hspace{0.17em}}\frac{\mathit{p}\left(1-\mathit{p}\right)}{{\left(\frac{d}{z_{\alpha }}\right)}^2}$. Data from the study showed that mumps virus nucleic acid test positivity rate was 31% (P = .31).¹⁷ With a significance level α = 0.05 and an allowable error d = 0.1, the required sample size N was at least 82.

Laboratory detection methods

The PCR detection was performed on PDS specimens using the Beijing JinHao Mumps Virus RNA Detection Kit, which employs a one-step, real-time fluorescent quantitative reverse transcription PCR (RT-qPCR) technique: extracted RNA is directly added to a single-tube reaction where reverse transcriptase synthesizes cDNA and, in the same closed system, Taq DNA polymerase amplifies the mumps-specific sequence while fluorescence is continuously monitored; the resultant Ct values are then used for absolute quantification by interpolation from an internal standard curve, and final positive/negative calls are made according to the real-time amplification curve morphology.¹⁸ The IgM/IgG antibody in case serum samples was quantitatively detected using the mumps virus IgM/IgG antibody detection kit (enzyme-linked immunosorbent assay, ELISA) from Virion & Serion, Germany.

Statistical analysis

In this study, WPS 2016 was used for data organization and visualization analysis. A segmented regression model was constructed using Joinpoint Regression Program 5.3.0. The temporal trend of the reported incidence rate of mumps from 2005 to 2024 was analyzed. Monte Carlo permutation tests were employed to identify non-linear trend inflection points. The Annual Percent Change (APC) for each trend segment and the overall Average Annual Percent Change (AAPC) were calculated to quantify the incidence rate change rates in different periods.¹⁹ The significance level α is 0.05.

Results

Epidemiology of mumps cases from 2005 to 2024

A total of 8,070 cases of mumps were reported from 2005 to 2024, including 4,833 males and 3,237 females. The average annual incidence rate (per 100,000 population) was 12.69 over 20 y. Highest incidence in 2006 (33.63), decreasing to 16.59 in 2010 after incorporation two-dose MMR in 2006, with a small rebound in 2011 and 2012, and continuing to decrease to 5.94 in 2019, until the lowest in 2024 (2.06) after incorporation three-dose MMR in June 2020. The AAPC (95% CI, P) of the reported incidence rate of mumps in the entire population from 2005 to 2024 was −13.47% (−15.09% to −11.65%, P < .01), with an inflection point in 2021. The APC (95% CI, P) of the reported incidence rate was −11.35% (−12.66% to −10.04%, P = .03) from 2005 to 2021 and −23.97% (−40.32% to −13.01%, P < .01) from 2021 to 2024. Changes in the number and incidence of mumps in 2005–2024 are shown in Figure 1.

Figure 1.

Changes in the number and incidence of mumps in 2005–2024.

Over the 20-y period, the incidence rate of males ranged from 2.36 to 43.06, with a mean ± standard deviation of 15.23 ± 11.38; for females, the range was 1.77 to 24.61, with a mean ± standard deviation of 10.53 ± 7.03. The annual incidence rate in males was consistently higher than that in females (t = 4.419, P < .01), and the results of the generalized estimating equation (GEE) were consistent: after adjusting for the effect of time, the incidence rates in both males and females showed a decreasing trend over time (P < .01), with males experiencing a faster decline (P < .01). However, the annual incidence rate in males remained higher than that in females (P < .01). The population shows a trend toward younger age groups, with children aged 0–10 y making up 70.54% (5,693 cases) of the total 8,070 cases. This includes 0–5 y (40.2%, 3,245 cases) and 6–10 y (30.3%, 2,448 cases). The 11–15 age group accounts for 8.5% (684 cases). For those aged 16 and above, the proportions are significantly lower: 16–20 y (3.5%, 280 cases), 21–25 y (4.0%, 322 cases), 26–30 y (4.3%, 347 cases), and 31 and above (9.2%, 744 cases).

Case data of the Isolation Surveillance Pilot Project from 2019 to 2024

Basic information

In this pilot project, a total of 146 participants were involved. Among them, 82 were male and 64 were female, resulting in a male-to-female ratio of 1.28. The average age of the participants was 8.16 y old, with the youngest participant being 2 y old and the oldest being 41 y old. The majority of the participants were children in childcare or students, accounting for 95.89% of the total cases (140/146) (Table 1).

Table 1.

Mumps cases characteristics in the Isolation Surveillance Pilot Project 2019–2024.

CASES	No. of patients (n=143)	%
Gender
Male	82	56.16
Female	64	43.84
Age group (years)
≤5	48	32.88
6–7	40	27.40
8–17	52	35.62
≥18	6	4.11
Year
2019*	17	11.64
2020	14	9.59
2021	54	36.99
2022	32	21.92
2023	20	13.70
2024	9	6.16
Classification by Role
Children in childcare	57	39.04
Students	83	56.85
Others	6	4.11
Vaccination status
Non-vaccinated	0	0.00
One MMR dose	53	36.30
Two MMR doses	88	60.27
Unknown	5	3.42
Time since last dose of MMR vaccine
0–5 y	120	85.11
≥6 y	21	14.89
Clinical Manifestations
Fever	36	24.66
Headache	16	10.96
Parotid swelling	146	100.00
Unilateral	127	86.99
Bilateral	19	13.01
Concomitant swelling of other salivary glands**	7	4.79
Parotid pain	125	85.62
Complications	0	0.00
Duration of parotid swelling (days)
1	20	13.70
2	25	17.12
3	22	15.07
4	21	14.38
5	11	7.53
6–7	25	17.12
8–9	18	12.33
10–12	4	2.74
Laboratory tests (No. of positive)
RT-qPCR assays	146 (4)	100.00
IgM assays	116 (6)	79.45
IgG assays	97 (96)	66.44

*From October 2019, not a full year.

**Other salivary glands were submandibular gland or sublingual gland.

Case classification

Among the 146 cases, 27 cases (18.49%) were laboratory-diagnosed, including 4 cases positive by PCR, 6 cases positive for IgM antibodies, and 18 cases with a fourfold or more increase in IgG antibody titers in paired sera. Among these, one case was positive by PCR and also had a fourfold or more increase in IgG antibody titers in paired sera. The remaining 119 cases were clinically diagnosed, with negative PCR results from at least two PDS tests.

Vaccination status

About 141 cases (96.58%) had received at least 1 dose of MMR vaccine, of which 88 cases had received 2 doses of MMR vaccine. Five cases, aged 30–41 y, were uncertain about their MuCV vaccination history. Among the cases, 85.11% experienced mumps within 0–5 y after receiving the last dose of MMR vaccine, indicating that the majority developed vaccine-preventable infectious diseases within 5 y post-vaccination (Table 1).

Clinical manifestations

All cases exhibited parotid gland swelling to varying degrees, with 19 cases presenting bilateral swelling and 127 cases showing unilateral swelling. Seven cases had parotid swelling concurrent with enlargement of other salivary glands (e.g., submandibular or sublingual glands), and 125 cases were accompanied by parotid pain. Additionally, 36 cases experienced fever of varying severity, with the highest recorded temperature being 40.4°C and the longest duration of fever lasting 9 d (median = 3, interquartile range, IQR = 2–4). Sixteen cases reported headaches. No cases developed complications such as mastitis, oophoritis, orchitis, or meningitis (Table 1).

The duration of parotid swelling ranged from 1 to 12 d (median = 4, IQR = 2–7). Specifically, 97.26% of cases had swelling lasting no more than 9 d, and 67.81% lasting no more than 5 d, and 30.82% between 1 and 2 d. Only four cases had parotid swelling lasting longer than 9 d. PCR tests on PDS in these cases were all negative, but one case tested positive for IgM antibodies in serum, confirming a laboratory-diagnosed case (Table 1).

Laboratory tests

Among the 146 cases, each case had at least two PDS samples collected, totaling 526 PDS specimens. PCR testing confirmed four laboratory-diagnosed cases. The positive specimens were subjected to further viral isolation and culture, and the results were all negative. Additionally, 116 cases underwent serum IgM antibody testing, with 6 cases meeting the laboratory diagnosis criteria. Ninety-seven cases underwent serum IgG antibody testing, with the results showing that: 96 cases had at least one positive IgG antibody test (the other was inconclusive or missing); One case had only one serum sample, which tested negative; 82 cases had both paired serum IgG antibodies positive; However, only 18 cases showed a fourfold or greater increase in paired serum IgG antibody titers (Table 1).

A total of 526 PDS were collected from cases and tested by RT-qPCR, and the overall positive rate was 1.14% (6 of 526) (Figure 2). On days 0–1, 2–3, 4–5, and 6–7 after parotitis onset, 1.69% (1 of 59 specimens positive), 4.41% (3 of 68), 0.00% (0 of 27) and 1.68% (2 of 119) of specimens, respectively, were positive, and all 253 specimens tested after 8 d were negative.

Figure 2.

Results of mumps tested by RT-qPCR by timing of specimen collection.

Quarantine duration

In this study, we analyzed the isolation duration of 146 mumps cases using two criteria: parotitis onset date and illness onset date. When defined by parotitis onset, the median duration of isolation was 7 d (IQR = 6–7). About 10.96% (16 cases) had isolation durations of not greater than 5 d, 83.56% (122 cases) had durations of 6–9 d, and 5.48% (8 cases) had durations of 10–14 d. When defined by illness onset, the median duration of isolation was 7 d (IQR = 6–8). About 8.22% (12 cases) had not greater than 5 d, 80.14% (117 cases) had 6–9 d, and 11.64% (17 cases) had 10–15 d. Notably, 77.40% (113 cases) had coincident parotitis and illness onset dates, resulting in identical isolation durations under both methods. For the remaining 22.60% (33 cases) with illness onset preceding parotitis onset by 1–7 d, isolation durations were systematically longer when calculated from illness onset. Despite these differences, both methods significantly reduced isolation durations compared to the current 21-d protocol: 88.36% (129 cases) had isolation periods shortened by 12 d (from 21 to 9 d), with all cases experiencing at least a 6-d reduction.

Discussion

Since mumps vaccine entered Beijing’s EPI in 2006, the incidence of mumps in Chaoyang District has decreased by 93.87% in 20 y, falling to 2.06/100,000 in 2024, which is consistent with the national and global trends of mumps prevention and control.^4,7,10 The annual percent change accelerated from −11.35% (2005–2021) to −23.97% (2021–2024) after the June 2020 launch of the three-dose MMR schedule. A transient rebound in 2011–2012 was driven by waning antibodies 5 y after the 2006 two-dose introduction and by gaps in second-dose coverage among migrant children. These two factors may combined to drive the brief rebound, which was quickly reversed through intensified outbreak control and catch-up vaccination, returning incidence to its downward trajectory. The present study found that males experienced 1.45-fold higher incidence than in females, consistent with Korean and Irish data.^20,21 In addition, the risk of mumps-related central nervous system complications is markedly elevated in males (≈3-fold),²² further underscoring males as a high-risk group. This disparity may be linked to lower post-vaccination antibody titers in males compared with females.²¹

Although post-vaccination outbreaks are reported elsewhere when immunity wanes or coverage is incomplete,^23–25 and a shift in the age distribution from children to adolescents or adults are reported,^23,26,27 Beijing has not reported any outbreaks since 2015,¹⁶ and Chaoyang District has not experienced any clustered cases since 2019 and cases remain predominantly concentrated under the age of 10, with no observed trend of increasing age distribution.

In this study, we investigated 201 close contacts of cases from childcare centers and schools (defined as individuals seated around the index cases). Except for one individual with a contraindication, all contacts had received ≥1 dose of MMR vaccine. No secondary cases were identified during the mumps incubation period (14–25 d), and no secondary transmission occurred in the collective settings after the index cases were released from isolation (secondary attack rate, 0%). This finding is consistent with international studies, which show that two doses of the vaccine can reduce the secondary attack rate to 2.2%–8.1%, representing a reduction of 86%–93% compared to unvaccinated populations.^28–31

A study on seronegative healthcare workers who had previously received two doses of MMR vaccine showed that the third dose can induce a strong immune response.³² A systematic review among healthcare workers emphasizes the medium and long-term immune protection provided by the three-dose MMR vaccine should be sufficient.³³

Vaccination not only reduces morbidity, but also significantly changes the characteristics of the disease: studies demonstrate that vaccinated cases exhibit milder clinical manifestations (e.g., significantly reduced rates of fever, parotid pain, bilateral parotid swelling, and complications), shorter duration of illness, and lower transmissibility compared to unvaccinated population.^34,35 With the establishment of mumps immunity and changes in disease characteristics, global isolation policies have been dynamically adjusted. The United States has been using the attenuated mumps vaccine for over 50 y.³⁶ Considering contagiousness and compliance, the isolation period was reduced from 9 d to 5 d in 2008.^37,38 Five-day isolation recommendations after symptom onset have also been made by WHO and the United Kingdom.^39,40 In Chaoyang, the new policy increased patient compliance by 83% and reduced related complaints by 76% with no secondary cases, demonstrating that high coverage makes shorter isolation both effective and acceptable. By leveraging primary-care networks – community centers working with schools and families – Chaoyang shortened isolation while sustaining control, illustrating that stronger frontline services make evidence-based, socially acceptable quarantine feasible (as argued in “The road to achieving epidemic-ready primary health care”).⁴¹

The shedding period of MuV extends from 7 d before symptom onset to 8 d after parotitis, with viral load peaking early in the illness and then rapidly declining.⁴² International studies have shown that in the United States, among outbreak groups with a 95% coverage rate of two doses of MMR vaccine, the PCR positivity rate for buccal mucosa samples was 35% during the first 0–3 d of parotitis, with no virus detected after day 4.^37,43 Systematic reviews have also confirmed that the window for positive MuV isolation in culture is within the first 0–6 d of parotitis.⁴² In this study, 526 PDS samples were tested. The PCR positivity rate was 3.15% (4/127) during the first 0–3 d of parotitis and 2.60% (4/154) during the first 0–5 days. No virus was detected after day 7, and no extended shedding period was observed. The shedding duration in all 27 laboratory diagnostic cases did not exceed the current 21-d isolation period. The above results support the feasibility of reducing the isolation period. However, the PCR positivity rate was lower than that reported in international studies. The differences in positivity rates may be attributed to the following factors: the current mumps diagnostic criteria (2007 edition) do not include PCR testing and lack exclusion criteria, which may lead to misdiagnosis of non-mumps cases; a high vaccination coverage rate (≥96.58% in this study) may reduce viral load below the detection threshold.

Current research has also revealed two major challenges in China’s diagnostic criteria for mumps: First, the existing criteria (2007 edition) do not incorporate PCR testing, leading to overdiagnosis in clinical settings (in this study, the PCR positivity rate during the early stages of illness was only 2.60%). Second, the lack of exclusion criteria means that a negative PCR result cannot correct the diagnosis. This suggests that the actual incidence of mumps in China may be overestimated, which in turn affects the accuracy of vaccine efficacy assessments. While WHO recommends two MMR doses,⁴⁴ Finland has become the first country eliminated mumps with a 14–18-month/6-y schedule,⁴⁵ the US, France, and Australia have recommended adding booster doses for adolescents or adults.^26,27,46 Beijing’s three-dose program, maintained above 95% coverage for 4 y, should yield even lower incidence.⁴⁷

The 21-d quarantine standard is outdated in light of evolving epidemiology; we therefore recommend adopting molecular diagnostic criteria, validating a ≤5-d quarantine via multicentre studies, and establishing dynamic vaccine-efficacy monitoring for targeted prevention. Drawing on global experience, two risks demand vigilance: immunity gaps in college students and adults – stemming from missed boosters or antibody decay – and accelerated transmission in dense settings, as underscored by an Indian study showing such gaps fuel resurgences and heavier quarantine burdens.⁴⁸ Implementation should maintain childhood schedules while dynamically monitoring and boosting key groups, and promptly updating the diagnostic standards by establishing a molecular diagnostic gold standard, refining exclusion criteria, and conducting multi-center validation studies.

Research limitations and future directions

This study has three limitations. First, the sample was confined to Chaoyang District, Beijing, and there is a need to expand the geographical representativeness. Second, it is necessary to use other methods or technologies, such as case-control detection studies and sequencing techniques, to confirm the etiological mechanisms underlying the low PCR positivity rate. Third, the reasons for vaccine failure with two doses need to be explored in depth. Future work is recommended to include: (1) a multicenter cohort study across the country to validate the adjustment of isolation periods; (2) the establishment of a monitoring system for vaccine breakthrough infections; and (3) research on viral genetic evolution and vaccine matching.^23,24

Biographies

Jian Zhang, Master of Public Health from Peking University and a Deputy Chief Physician in Preventive Medicine. She has been engaged in the prevention and control of infectious diseases and the surveillance of vaccine-preventable diseases for nearly two decades. During her career, she has participated in the handling of multiple public health emergencies and outbreaks of infectious diseases, accumulating extensive experience in on-site response. She has also led research projects funded by the district science and technology committee and participated in numerous important national and municipal research projects, publishing over 10 scientific papers.

Bin Jia, Master of Public Health from Peking University, is the Chief Physician of Preventive Medicine. Jia leads the Department of Planned Immunization of the Beijing Chaoyang District Centre for Disease Control and Prevention. With over two decades of experience, Jia specia lizes in immunization planning and the surveillance of vaccine- preventable diseases. Jia has been a principal investigator in numerous significant research initiatives, including projects funded by the Beijing Natural Science Foundation, the National Center for Disease Control and Prevention, the Beijing Municipal Center for Disease Control and Prevention, and the Science and Technology Commission of Beijing Chaoyang District. He has authored more than 20 scientific papers, contributing extensively to this field.

Funding Statement

The author(s) reported that there is no funding associated with the work featured in this article.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Abbreviations

MuV

mumps virus

NNDRS

National Notifiable Disease Reporting System

MuCV

mumps-containing vaccine

NIP

National Immunization Program

MMR

measles-mumps-rubella combined attenuated vaccine

CDC

Center for Disease Control and Prevention

CYDES

Chaoyang Digital Epidemiological Survey System

PCR

Polymerase Chain Reaction

PDS

Parotid duct swabs

RT-qPCR

real-time fluorescent quantitative reverse transcription PCR

ELISA

enzyme-linked immunosorbent assay

APC

Annual Percent Change

AAPC

Average Annual Percent Change

IQR

Interquartile Range

Ethical statement

The data analyzed in this study were obtained from the routine infectious disease surveillance system managed by the Chaoyang District Center for Disease Control and Prevention (Beijing, China). These data are collected as part of mandatory public health reporting and are fully anonymized at the source. According to the Ethical Review Measures for Biomedical Research Involving Humans (National Health Commission, China, 2023), studies utilizing such surveillance data for public health purposes are exempt from ethical review.⁴⁹ No individual patient consent was required.