Epidemiological characteristics and survival analysis of pertussis in Quzhou

ABSTRACT

Despite high vaccination coverage in high-income countries, recent reports of pertussis resurgence have heightened public concern about vaccine effectiveness and vaccination. Quzhou City has gradually transitioned from DTwP to DTaP vaccines, achieving a remarkable vaccination coverage rate of 99%. However, since 2024, there has been a significant surge in pertussis cases in Quzhou City. We collected data on pertussis cases, described the epidemiological characteristics of pertussis outbreaks in Quzhou City, examined pertussis vaccination history, and conducted a COX survival analysis. Pertussis cases reported in Quzhou City from January to April 2024 were far higher than those reported in previous years during the same period. Geographically, cases were concentrated in the central region and predominantly affected children under 9 years old, with a focus on the 5–9 age group. Survival analysis revealed that the risk of pertussis incidence increased by 2.84 times (HR = 2.87, 95% CI = 2.27 ~ 3.63) when comparing self-paid vaccines to free vaccines. The pertussis situation in Quzhou City remains critical, emphasizing the need for enhanced immunization strategies and further optimization of pertussis immunization protocols.

Introduction

Pertussis, also known as whooping cough, is an acute respiratory infectious disease caused by the bacterium Bordetella pertussis. It is primarily transmitted through airborne droplets, making it highly contagious.¹ It typically manifests as paroxysmal spasmodic coughing. Many countries have implemented multi-dose immunization programs that include the pertussis component vaccine. However, in the past few decades, the incidence of pertussis has increased in some developed countries,^2,3 a phenomenon referred to as the “resurgence of pertussis.”⁴ In particularly, there has been a significant increase in cases among individuals over the age of 10 years, with a rising incidence rate in adolescents.⁵ For example, in 2019, the United States reported 18,617 cases of pertussis, resulting in 7 deaths. The incidence rate per 100,000 people was highest in infants under 6 months old (76.5), and 4 of the 7 deaths occurred in infants under 1 year of age.⁶

Vaccination against pertussis is the most effective method of prevention. In 1978, China included the Diphtheria, tetanus and whole-cell pertussis combined vaccine (DTwP) into its routine immunization program.⁷ Since 2007, China has gradually replaced the DTwP with Diphtheria, tetanus and acellular pertussis combined vaccine (DTaP).⁸ The full course of DTaP immunization consists of four doses, administered at 3 months, 4 months, 5 months, and 1.5 years of age. After the complete replacement with the DTaP vaccine in 2013, the incidence of pertussis decreased significantly in China. However, since 2010, the reported incidence rate has increased each year.^7,8 It has been 46 years since the pertussis vaccine was included in the routine immunization program, and the incidence of pertussis has been well controlled. However, the “resurgence of pertussis” has received widespread attention in the past decade.

Quzhou City began implementing the Expanded Program on Immunization (EPI) in 1980. From 1980 to 1989, the city used non-adsorbed DTwP; from 1990 to 2007, adsorbed DTwP was used. In 2008, Quzhou started implementing the expanded national immunization program, gradually replacing DTwP with DTaP. During the transition period (for children born between May 1, 2006, and July 1, 2008), children received 3 doses of DTwP and 1 dose of DTaP. Children born after July 1, 2008, received 4 doses of DTaP. The various DTP immunization schedules all included a primary series of 3 doses at 3–6 months of age and a booster dose at 18–24 months of age.⁹ The incidence of pertussis in Quzhou City has remained at a relatively low level over the years, with a vaccination coverage rate as high as 99%. However, since 2024, there has been a sudden surge in pertussis cases, far exceeding the historical average. The protection of pertussis vaccine has raised widespread concern. In this study, we collected data on pertussis cases to describe the basic epidemiological situation in Quzhou City, conducted a Cox survival analysis to evaluate the effectiveness of different types of pertussis vaccines, and provided a basis for revising pertussis vaccination strategies.

Materials and methods

Study design

Quzhou is a prefecture-level city in the western part of Zhejiang Province, China, located at the junction of four provinces, providing convenient transportation access. It is situated in the western section of the Jinqu Basin, characterized mainly by mountainous and hilly terrain. The city has a subtropical monsoon climate with distinct seasons and abundant rainfall. As of the end of 2023, Quzhou had a permanent resident population of 2.297 million and a registered population of 2.55 million. The birth rate in 2023 was 5.3‰, reflecting a decrease of 0.2‰ compared to 2022.

The study collected data on reported pertussis cases and vaccination status from 2006 to April 2024. A descriptive analysis and Cox regression analysis were conducted to provide a reference for optimizing the pertussis immunization program. The research design is illustrated in Figure 1.

Figure 1.

The overall study design of epidemiological characteristics and survival analysis of pertussis in Quzhou.

Data sources

In April 2024, data on cases of pertussis in Quzhou City from January 1, 2006 to April 16, 2024, were collected from the China Disease Prevention and Control Information System. The selection criteria were as follows: 1) Disease name: Pertussis; 2) Report review time: January 1, 2006, to April 16, 2024; 3) Current address: Quzhou City; 4) Review status: Reviewed. The case information included basic information and the onset time. Vaccination information was obtained from the Zhejiang Province Immunization Program Smart Service Information System. Data were collected on the pertussis vaccination history of pertussis cases, including the type of pertussis vaccine (whole-cell, acellular, quadrivalent, pentavalent) and the timing of the first, second, third, and fourth doses. Information from the two systems was matched using ID number, case name, and telephone number, and integrated to create a database of pertussis incidence and vaccination in Quzhou City from 2006 to 2024. Demographic data were obtained from the Quzhou City Statistical Yearbook.

Case definition

According to the Diagnostic Criteria for Pertussis (WS274–2007), pertussis cases include clinically diagnosed cases and confirmed cases. The clinical manifestations of pertussis are as follows: (1) Paroxysmal spasmodic cough during the epidemic season; (2) Cough accompanied by vomiting, with severe cases showing subconjunctival hemorrhage or tongue frenulum ulcers; (3) Unexplained paroxysmal cyanosis or choking in newborns or infants, typically presenting as classic pertussis; (4) Persistent cough for more than two weeks, excluding other causes.

A clinically diagnosed case is defined as the presence of any of the above clinical manifestations are present, or if there is a combination of “contact with a pertussis patient within three weeks, or an outbreak of pertussis in the area,” and “a significantly elevated white blood cell count with a lymphocyte proportion >0.5.”

A confirmed case is defined as clinically diagnosed case plus isolation of Bordetella pertussis from the patient’s sputum or pharyngeal swab, or a four-fold or greater increase in serum agglutinating antibody levels during the convalescent phase compared to the acute phase. A single Pertussis toxin (PT) IgG antibody concentration (titer) greater than the guideline-recommended threshold for diagnosis of acute infection applies to children, adolescents, and adults one year after vaccination with a pertussis-containing vaccine.¹⁰

Related definition

Completion of basic immunization refers to receiving three doses of pertussis vaccine, which may include three doses of whole-cell, acellular, quadrivalent, or pentavalent pertussis vaccines. Full course immunization refers to receiving four doses of pertussis vaccine, which includes the three doses from basic immunization plus one additional booster dose.

Survival analysis will be used to study the relationship between different immunization schedules with various types of vaccines and the incidence of pertussis, as well as their long-term protective effects. In this study, the baseline events are the administration of the third and fourth doses of pertussis vaccine to the subjects. The endpoint is the subject’s diagnosis of pertussis. The observation period ends on April 16, 2024. The duration of vaccine protection for individuals who develop the disease is calculated as the time elapsed between the administration of the third or fourth dose of pertussis vaccine and the onset of the disease.

Statistical analysis

A database of pertussis reported cases in Quzhou City was established using Excel 2013. Statistical analysis was conducted using R 4.3.1 software. The age of onset was represented as a range; categorical data were presented as composition ratios/rates. Comparison between groups was performed using the χ² test and χ² trend test. The formula for calculating the incidence rate from 2006 to 2024 is as follows: Incidence rate (/100,000) = (Number of cases/Total population) × 100,000. Survival data were analyzed using the Kaplan-Meier (K-M) method to plot survival curves, and the log-rank test was used to assess survival differences. A Cox proportional hazards model was used for multivariate analysis to evaluate the effects of different factors. All tests were two-sided, with a significance level of p-value <.05.

Results

Basic information

From January 1, 2006, to April 16, 2024, a total of 681 cases of pertussis were reported in Quzhou City, with an annual reported incidence rate ranging from 0 to 80.29 per 100,000. No deaths were reported (Figure 2).

Figure 2.

Incidence and reported cases of pertussis in Quzhou City from 2006 to 2024.

Epidemiological characteristics

Temporal distribution

From 2006 to 2023, the number of case reports has consistently remained below 50 cases. However, starting in 2024, there has been a notable increase in reported cases, with the highest number reaching 539 cases as of April 16, 2024 (Table 1). From 2006 to 2023, the number of reported cases primarily peaked during the months of April to September and November to December. The cases began to rise from January to June, reaching a peak of 19 cases in June, followed by fluctuations and a decline, with a rebound and increase observed from November to December (Table 1).

Table 1.

Distribution of pertussis cases in different months in Quzhou city from 2006 to 2024.

Year	Month
	1	2	3	4	5	6	7	8	9	10	11	12	Total
2006	0	0	0	0	0	0	0	0	1	0	0	0	1
2007	0	0	0	0	0	1	0	0	0	0	0	0	1
2008	1	0	1	1	0	0	0	0	0	0	0	0	3
2009	0	0	0	0	0	1	0	0	0	0	0	0	1
2010	0	0	0	1	0	0	0	0	0	0	0	0	1
2011	0	0	0	0	0	1	1	1	0	0	0	0	3
2013	0	0	0	0	0	0	0	0	0	0	2	0	2
2014	0	0	0	1	1	1	0	0	1	0	0	0	4
2016	0	0	0	0	1	0	1	1	0	0	0	0	3
2017	0	0	1	1	0	0	1	0	0	1	0	0	4
2018	0	0	1	3	3	2	2	2	3	0	1	0	17
2019	0	0	1	1	2	2	2	1	1	0	1	2	13
2020	1	0	0	0	1	0	0	0	0	0	0	0	2
2021	0	0	0	0	0	0	0	0	0	0	0	1	1
2022	0	3	2	2	7	6	3	4	7	0	1	1	36
2023	1	0	1	0	3	5	5	8	3	7	7	10	50
2024	12	21	111	395	–	–	–	–	–	–	–	–	539
Total	15	24	118	405	18	19	15	17	16	8	12	14	683

“-” indicates data not yet available.

Regional distribution

In Quzhou City, pertussis cases are distributed across 6 counties (cities, districts). From 2006 to 2023, the highest and lowest total cases were in Changshan County and Kaihua County, with 43 and 9 cases respectively. In 2024, the highest and lowest total reported cases were 234 in Jiangshan and 43 in Qujiang, respectively (χ² _trend = 62.696, p < .05, Table 2). Pertussis cases in Quzhou City are mainly distributed in the central region, with fewer reported cases in the eastern and western regions. The hotspot areas for cases have shifted from Changshan County in the earlier period to Kecheng District in the later period (Figure 3).

Table 2.

Statistical distribution of pertussis cases in different categories in Quzhou city from 2006 to 2024.

Characters		2006—2023 Year		2024 Year		χ2	P
		No.	%	No.	%
Country						62.696	<0.05
	Kecheng	24	16.90	234	43.41
	Qujiang	21	14.79	43	7.98
	Changshan	43	30.28	51	9.46
	Kaihua	9	6.34	48	8.91
	Longyou	22	15.49	77	14.29
	Jiangshan	23	16.20	86	15.96
Age(year)						82.031	<0.05
	0—4	97	68.31	151	28.01
	5—9	41	28.87	292	54.17
	≥10	4	2.82	96	17.81
Gender						1.5173	>0.05
	Male	67	47.18	288	53.43
	Female	75	52.82	251	46.57

Figure 3.

Regional distribution of pertussis cases in Quzhou City. (a) Regional distribution of pertussis cases in Quzhou City from 2006 to 2023. (b) Regional distribution of pertussis cases in Quzhou City from 2024.

Population distribution

In Quzhou City from 2006 to 2024, the reported age range of pertussis cases ranged from 22 days to 76 years. The proportion of cases in the 0–4 years age group decreased from 68.31% (97/142) in 2006–2023 to 28.01% (151/539) in 2024, while the proportion of cases in the 5–9 years age group showed the opposite change, increasing from 22.87% (41/142) to 54.17% (292/539), while the range of percentage change in the ≥10 years age group was relatively flat (χ² _trend = 82.031, p < .05, Table 2). There were 355 male pertussis cases and 326 female cases in Quzhou City, with a male-to-female ratio of 1.09:1.00. The male-to-female ratio during 2006–2023 was 0.89:1.00, and in 2024 it was 1.15:1.00, with no statistically significant trend (χ² _trend = 1.5173, p > .05, Table 2). The top three occupations in all cases of pertussis are scattered children, preschool children, and students, accounting for 28.93% (197/681), 32.01% (218 cases), and 33.77% (230 cases), respectively.

Pertussis vaccination status

Through individual case investigations, among the 681 cases, 86.64% (590 cases) had a history of receiving pertussis vaccine, while 13.36% (91 cases) had no vaccination history, all with unknown vaccination status. Of the 590 cases with a vaccination history, 527 cases received 4 doses, 31 cases received 3 doses, 12 cases received 2 doses, and 20 cases received 1 dose of vaccine. Among eligible children, the vaccination rate for 3 doses or more of the vaccine in cases over 3 months old were 87.37% (588/673), and the vaccination rate for 4 doses of the vaccine in cases over 18 months old was 86.68% (527/608) (Table 3).

Table 3.

Pertussis vaccine coverage among pertussis cases of different ages in Quzhou City from 2006 to 2023 [cases (%)].

Vaccine doses	<3 Months	3~11 Months	12~17 Months	18 Months ~5Year	6~14 Year	≥15 Year	Total
0	8(8.79)	20(21.98)	1(1.10)	2(2.20)	19(20.88)	41(45.05)	91(100.00)
1	0(0.00)	16(80.00)	1(5.00)	2(10.00)	1(5.00)	0(0.00)	20(100.00)
2	0(0.00)	10(83.33)	1(8.33)	0(0.00)	1(8.33)	0(0.00)	12(100.00)
3	0(0.00)	9(29.03)	7(22.58)	12(38.71)	1(3.23)	2(6.45)	31(100.00)
4	0(0.00)	0(0.00)	0(0.00)	183(34.72)	339(64.33)	5(0.95)	527(100.00)
Total	8(1.17)	55(8.08)	10(1.47)	199(29.22)	361(53.01)	48(7.05)	681(100.00)

Survival analysis

The Cox regression analysis of pertussis cases who completed primary and full immunization is shown in Figure 4. The results indicated that there was no statistically significant difference in gender and region for both primary and full immunization (p > .05); however, the type of vaccine (self-pay vaccines including quadrivalent, quintivalent vaccines vs. free vaccines) showed statistical significance (p < .05). The risk of pertussis infection was 2.87 (95% CI = 2.27-3.63) and 1.42 (95% CI = 1.09-1.90) times higher for primary and full immunization with self-pay vaccines, respectively, compared with those who received free vaccines.

Figure 4.

Forest plot of primary and full course immunization.

The survival analysis flowchart is shown in Figure 5, which showed results similar to those in Figure 4.

Figure 5.

Log rank analysis plot of primary immunization and full course immunization.

Discussion

The burden of pertussis among infants and young children is severe on a global scale.¹¹ The reported cases of pertussis in Australia increased by more than 100 times from 1991 to 2011.¹² In 2010, California, United States reported over 9,000 cases, the highest in nearly 60 years.¹³ From 2008 to 2010, the annual reported cases of pertussis in Japan were 2.7 times higher than the average of the previous five years.¹⁴ In China, the reported incidence rate of pertussis in 2019 was as high as 2.15 per 100,000, approximately 10 times higher than the average reported incidence rate from 2006 to 2010.⁴ Other regions have also experienced local outbreaks and resurgence of pertussis. In Anhui province, a significant increase in pertussis cases has been observed since 2017, with the reported incidence numbers in 2018 and 2019 increasing by 2.22 and 4.06 times respectively compared to 2017.¹⁵

By analyzing the trends in reported pertussis cases in Quzhou City from 2006 to April 16, 2024, it can be observed that prior to 2018–2019 and 2022–2023, where there were slight increases in reported cases, pertussis cases remained at relatively low levels. However, starting from 2024, pertussis cases in Quzhou City have exhibited an outbreak trend, surpassed historical averages and indicated a resurgence of pertussis. Current domestic and international research suggests that the reasons for the pertussis resurgence may include the evolution of Bordetella pertussis under vaccine selection pressure, particularly following the use of acellular pertussis vaccines¹⁶; the waning of vaccine-induced immunity is more pronounced with acellular pertussis vaccines^13,17; transmission caused by asymptomatic carriers of pertussis¹⁸; improvements in pertussis monitoring and diagnostic methods. Foreign studies also suggest that acellular pertussis vaccines may not induce lifelong immunity. For example, in Canada, the significantly increased incidence of pertussis may be attributed to the waning of vaccine protection over time.¹⁹ The resurgence of pertussis in Quzhou City may be related to the transition from whole-cell to acellular pertussis vaccines that took place gradually from May 1, 2006, to July 1, 2008. Further evaluation is needed to determine the potential impact of this vaccine transition on the reemergence of pertussis.

In recent years, the increasing incidence rate of pertussis reports may also be related to the application of rapid diagnostic method PCR in some hospitals.²⁰ After the introduction of highly sensitive pertussis PCR testing in Toronto, Canada in 2006, the number of case samples submitted for testing increased sixfold, leading to a fivefold increase in pertussis incidence rates.²¹ Through sentinel hospital case monitoring in cities such as Tianjin, Jinan, and Kaifeng in China, it has been discovered that the reporting levels of pertussis cases have been significantly underestimated, with a notable increase in cases among adults and adolescents.²² Before 2024, pertussis cases in Quzhou City were primarily diagnosed clinically, lacking laboratory diagnostic capabilities. Similar to other cities, underreporting of cases in hospitals led to an underestimation of the pertussis epidemic. However, since early 2024, the Zhejiang Provincial Clinical Testing Center has mandated pertussis Bordetella pertussis nucleic acid testing. The Zhejiang Provincial CDC has established pertussis monitoring programs and conducted special investigations, clarifying case definitions and classifications to standardize the reporting and management of pertussis cases. Subsequently, some hospitals in Quzhou City have gradually implemented laboratory testing, and healthcare workers have heightened awareness of pertussis diagnosis and reporting. This has improved the sensitivity of pertussis monitoring, potentially leading to an increase in reported pertussis cases.

During the COVID-19 pandemic, Quzhou, like other cities in China, implemented “dynamic zero” control measures, which included extensive public health interventions such as maintaining social distancing, reducing large gatherings, wearing masks, restricting movement, and promoting hand hygiene. These measures significantly reduced the transmission of respiratory infections,²³ including pertussis. Additionally, the stringent control measures led to the reallocation of many medical resources during the COVID-19 pandemic, resulting in interruptions to regular health services. This may have caused delays in the timely diagnosis and treatment of some pertussis cases, thereby affecting the incidence statistics.²⁴ Reports of pertussis cases in Quzhou also indicate a significant increase after the end of the COVID-19 pandemic, likely triggered by the easing of extensive public health interventions, which may have caused an outbreak. Furthermore, the number of reported pertussis cases during the pandemic years 2022–2023 was significantly lower than that from January to April 2024. This discrepancy may be attributed to changes in disease monitoring and reporting, as many public health institutions focused their resources on monitoring and responding to COVID-19, potentially leading to a reduction in the surveillance and reporting of other infectious diseases, including pertussis, which may have affected the observation and assessment of its incidence. Another important factor is the variation in pertussis vaccination rates. During the COVID-19 pandemic, vaccination campaigns in many countries were disrupted, particularly routine childhood vaccinations.²⁵ In Quzhou, the pertussis vaccine is typically administered during childhood, with doses given at 3, 4, 5, and 18 months of age as part of the combined diphtheria, tetanus, and pertussis vaccine. A decline in vaccination rates may lead to an increase in the incidence of this disease in the coming years.²⁶ Moreover, changes in social behavior during the pandemic have likely altered population immunity, resulting in fluctuations in herd immunity. An increase in the unvaccinated population may elevate the risk of pertussis transmission.

According to the World Health Organization (WHO), the age distribution of pertussis cases has shifted from primarily affecting infants to encompassing all age groups. The fastest growth in reported cases is observed in infants younger than 6 months old and in adolescent and adult populations.²⁷ In 2018, the European Union reported that individuals aged 15 and above accounted for 62% of all pertussis cases. The highest incidence rate was observed in infants under 1 year old (44.4 per 100,000), followed by the 10–14 age group (22.0 per 100,000).²⁸

The research findings indicate that in Quzhou City, the 5–9 age group accounted for nearly half of reported pertussis cases, while children aged 0–9 comprised close to 80% of cases. The proportion of cases in the 0–4 age group decreased significantly, with notable increases in the 5–9 and ≥10 years age groups. This may indicate that after 60 months of complete immunization, the pertussis antibodies have decreased to a level that is no longer protective, which is consistent with the high incidence observed in children aged 5 to 9 years.²⁹ There was no significant difference between males and females. Despite a trend of pertussis cases shifting from infants to children and adolescents, it is important to remain vigilant about the harm pertussis poses to young children, prevent severe complications and fatalities, and also consider the potential for adult-to-child transmission. Cases are primarily concentrated in children aged 0–9, most of whom attend daycare centers and schools, where the occurrence of a case can lead to rapid transmission. Therefore, it is crucial to enhance monitoring and reporting of pertussis cases in schools and daycare facilities, and in cases occurring in collective settings like primary and secondary schools, early diagnosis, treatment, and isolation should be implemented, along with ensuring proper morning and afternoon checks.

The research findings revealed that from 2006 to 2018, there were relatively few reported pertussis cases in Quzhou City, and no significant seasonal pattern was observed. However, from 2019 to 2023, the majority of cases occurred in the summer, with occasional cases in winter and spring. This pattern aligns with the overall trend of pertussis in China.³⁰ The sudden surge in reported pertussis cases in Quzhou City from January to April 2024, with a significant increase in cases in March and April (up to April 16th) compared to January and February, indicates an outbreak. The seasonal trend of pertussis in Quzhou City in 2024 requires further observation and research to understand the reasons behind this sudden escalation and to implement appropriate control and prevention measures.

In recent years, the majority of reported pertussis cases in Quzhou City have been concentrated in the central region, with fewer cases in the eastern and western regions. This distribution pattern may be attributed to the fact that medical institutions in Quzhou City have primarily focused on pertussis pathogen and serological testing, with a higher concentration of such facilities in tertiary medical institutions and the central region. The improvement in laboratory testing capabilities in the central region may be one of the contributing factors to the higher number of reported cases in that area.

Among cases aged 3 to 11 months, 88.36% (46/55) had received less than or equal to 2 doses of the vaccine. In the 6 to 14-year-old group, 94.74% (342/361) had completed 4 doses of the vaccine. This indicates that if vaccines are not administered in a timely and effective manner, the body may not produce sufficient antibodies to protect against infection. Furthermore, both natural infection and vaccination may not provide lifelong immunity,³¹ The primary function of vaccination is to reduce the likelihood of severe cases and death among infants and young children, but it may not effectively prevent infection or interrupt transmission. The duration of immunity conferred by vaccination is approximately five years.^13,32

Survival analysis studies have shown that the survival probability of free pertussis vaccines is higher than that of paid pertussis vaccines. The main difference between free and paid vaccines lies in the production process, with pertussis vaccines using a co-purification process and vaccines using a component purification process. The difference in efficacy between whole-cell and acellular pertussis vaccines may be attributed to the presence of a greater number of antigen components in the whole-cell pertussis vaccine.³³ However, further research is needed to determine the relationship between the purification process and the actual protective effectiveness of the vaccines. Some research results indicate that individuals vaccinated with initially component-purified vaccines have higher antibody titers compared to those vaccinated with co-purified vaccines. Nevertheless, based on antibody decay models, there is no significant difference in antibody levels between the two groups after 60 months.²⁹ After completing the full course of pertussis vaccination in Quzhou, there may be a longer interval between vaccination and disease onset. The protective effects of different types of vaccines may not be significantly different. Additionally, the detection and reporting of pertussis cases in Quzhou may not be comprehensive, with symptomatic cases being reported while asymptomatic cases may go unreported. There is a significant imbalance in the number of patients receiving two different vaccines, with a notably higher number of cases vaccinated with free vaccines compared to those vaccinated with paid vaccines. This imbalance may also contribute to the higher survival probability of free pertussis vaccines observed in survival analysis studies. Furthermore, pertussis is highly contagious, and there may be differences in exposure opportunities, necessitating further research on the spatiotemporal clustering of cases.

This article has certain limitations. Firstly, there are differences in monitoring and laboratory testing levels and quality in different regions, leading to variations in disease reporting. Secondly, the data primarily come from passive monitoring, which may result in incomplete case reporting. Thirdly, the study collected an uneven number of cases vaccinated with different pertussis vaccines, which could bias the results of survival analysis. Finally, this study didn’t include data on COVID-19 incidence and vaccination rates for analysis. Future research could explore these factors in greater depth.

Conclusion

The pertussis situation in Quzhou remains very serious. It is necessary to intensify the promotion of pertussis vaccination, conduct health education and knowledge dissemination, and reduce missed vaccinations and vaccine refusals. Further strengthening pertussis monitoring to improve sensitivity is crucial. Enhancing training for healthcare personnel to improve the standardization of pertussis case diagnosis and treatment is also recommended. Additionally, initiating active monitoring for pertussis and refining the immunization strategy for pertussis to optimize the immunization process further would be beneficial.

Biographies

Zheng Canjie male, postgraduate degree, deputy chief physician, now working in Quzhou Center for Disease Control and Prevention immunization planning section chief, long engaged in the implementation of the expanded immunization program and vaccine-targeted disease surveillance work, has published more than 10 academic papers.

Yin Zhiying she is the deputy director of Quzhou Center for Disease Control and Prevention, a member of the Standing Committee of Quzhou Science and Technology Association, a chief physician and a master’s tutor. She has been engaged in work related to immunization planning for 20 years, and is a new talent in medical field in Zhejiang Province and 115 talents in the city. She has participated in the writing and publication of 9 SCI papers, of which 6 were published by the first or corresponding authors. She has published many academic papers in Chinese core journals, including ”Analysis of Varicella Epidemic Characteristics and Varicella Vaccine Immunization Effect in Quzhou City, Zhejiang Province, 2006-2014”, which has been selected as one of the top academic papers in China’s top-quality Science and Technology Journals, ”Leader 5000”, by China Institute of Science and Technology Information (Certificate No. G452201604010). (Certificate No. G452201604010). She has presided over a number of provincial and municipal science and technology projects.

Funding Statement

The author(s) reported 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).

Author contributions

WX and CF,: Methodology, Visualization, Writing – original draft. ZY, XG, and QF: Data curation, Writing – review & editing. WX: Writing – review & editing.

Data availability statement

The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to WX 142,199,091@qq.com.

Ethical approval

Ethical approval for this type of study is not required by our institute.