Research and analysis

Laboratory confirmed cases of pertussis in England: annual report for 2023

Published 31 October 2024

Applies to England

Introduction

This document summarises data on laboratory-confirmed cases of pertussis reported in England in the calendar year 2023. The report covers confirmed case numbers and their distribution, information on deaths related to pertussis, and data on vaccination uptake through the childhood and maternal programmes. It builds on summary data from previous annual reports published by UKHSA.

Pertussis is a cyclical disease, with increases occurring every 3 to 5 years, and seasonal activity usually peaking each year in quarter 3 (July to September). A national increase in laboratory-confirmed cases of pertussis in England was observed in 2023 after very low disease levels in 2021 and 2022. This has continued into 2024. 

As noted in previous annual reports for pertussis, the COVID-19 pandemic and the implementation of social distancing measures and lockdown across the UK from 23 March 2020 had a significant impact on the spread and detection of other respiratory infections including pertussis. From July 2021 COVID-19 containment measures were withdrawn in England. 

Vaccination against pertussis, including maternal vaccination, and other infectious diseases continues to be important as increasing levels of these diseases are expected following the easing of control measures, and in light of increased case numbers observed especially towards the end of 2023.

Laboratory confirmed cases and incidence

In England, there were 856 new laboratory-confirmed cases of pertussis (tested via culture, PCR, serology or oral fluid) reported to the UK Health Security Agency’s (UKHSA’s) pertussis enhanced surveillance programme in 2023. This was substantially higher than the 68 cases reported in 2022, and the 49 cases in 2021, when population control measures were in place due to the COVID-19 pandemic. Total cases in 2023 were lower than pre-pandemic years when 994 and 3,680 cases were reported in 2020 and 2019, respectively (figure 1).

The total number of samples submitted to UKHSA for testing was 30% lower in 2023 (9,242) than in 2022 (13,128) with a test positivity rate of 8.1% (751 of 9,226) in 2023 compared with 0.6% (75 of 13,041) in 2022.

The number of cases reported varied by quarter. There were 29 confirmed cases in quarter 1, 106 cases in 2023 quarter 2, 267 cases in quarter 3 and 454 cases in quarter 4 (figure 1 and table 1). The increase in the number of confirmed cases has continued into 2024 and UKHSA declared a national (standard) incident for pertussis in England in May 2024. UKHSA continues to monitor the situation and data for 2024 is published monthly. The national incidence for all age groups, based on laboratory confirmed cases of pertussis in England and 2023 population estimates (1) was 1.5 per 100,000 in 2023 compared to 0.1 per 100,000 in 2022 and 2021, 1.8 per 100,000 in 2020 and 6.5 per 100,000 in 2019; it reached 17.5 per 100,000 in 2012 (epidemic peak year). Prior to the major peak in 2012, incidence ranged between 0.4 per 100,000 and 2.0 per 100,000 (figure 2).

There were 96 laboratory confirmed pertussis cases in infants aged under one year in 2023 compared to 5 cases reported in 2022 and 2 cases in 2021. This compares with 508 confirmed cases reported in the outbreak year in 2012. The number of confirmed cases in infants under one year of age in 2021 and 2022 were the lowest reported since the introduction of enhanced surveillance in 1994.

There has been a decline in pertussis incidence in infants under 3 months of age since the introduction of the maternal vaccination programme in 2012. The incidence rate has declined from 234 per 100,000 in 2012 to 93 per 100,000 in 2016, 20 per 100,000 in 2020 and 1.3 per 100,000 in 2022 (figure 2). Incidence in this age group increased to 33.5 per 100,000 in 2023, and was higher than any other age group in this year.

Forty-eight infants aged under 3 months were confirmed in 2023 compared to 2 cases in 2022 and 1 case in 2021 but case numbers remained lower than pre-pandemic cyclical peak years and lower than the 407 cases reported in the 2012 epidemic peak.

Similarly the number of of cases in infants aged 3 to 5 months increased from 3 cases (2 per 100,000) in 2022 to 23 cases (16.1 per 100,000) in 2023, but lower than the 74 cases (43 per 100,000) reported in 2012.

In the 2016 cyclical peak, confirmed cases aged between 6 and 11 months were higher (34 cases, 10.2 per 100,000) than in any year since the introduction of enhanced surveillance. In 2019 incidence in this age group was 6.8 per 100,000 (21 cases) and 1.7 per 100,000 (5 cases) in 2020. There were no reported cases in infants aged between 6 and 11 months in 2022 and in 2021.  In 2023, 25 cases (8.7 per 100,000) were reported in this age group. These low numbers are consistent with protection from primary vaccination offered at 2, 3 and 4 months of age.

Increases in confirmed case numbers were seen across all older child age groups in 2023 by comparison with 2022:

• the number of children aged 1 to 4 years confirmed with pertussis increased from 10 cases, in 2022, to 52 cases in 2023. Confirmed cases, in this age group in 2023, were lower than the 2016 and 2012 peak years when 117 and 103 cases, respectively, were reported
• in children aged 5 to 14 years, numbers of confirmed cases increased from 6 cases, in 2022, to 255 cases in 2023 but were lower than the 2016 (809 cases) peak years and 2012 (981 cases) outbreak
• laboratory confirmed pertussis cases in individuals aged 15 years and older increased from 47 cases in 2022 to 453 cases in 2023. Total cases in this age group were lower than the peak years when 4,787 cases were reported in 2016 and 7,775 cases in 2012. Half (53%; 453 of 856 cases) (table 2) of laboratory confirmed cases in England in 2023 occurred in individuals aged 15 years and older compared to 69% (47 of 68 cases) in 2022 and  80% (39 of 49 cases) in 2021

It should be noted that ascertainment in those aged 5 to less than 17 years has improved with availability of oral fluid testing since 2013. From 1 May 2018, the availability of oral fluid testing was extended to all children aged from 2 up to and including 16-year-olds, which may underpin earlier increases observed in the 1 to 4 year age group. In 2023 oral fluid alone accounted for 49% (149 of 307) of cases in children aged between 1 and 14 years.

Deaths

In England, 14 deaths were reported in infants with confirmed pertussis in the 2012 outbreak year. Following the introduction of pertussis vaccination in pregnancy there have been 21 further deaths in babies with confirmed pertussis to the end of 2023. There were no reported deaths in infants with confirmed pertussis between 2020 and 2022, and 1 death reported in 2023.

All the deaths in 2012, and those that occurred between the introduction of the maternal programme and end-December 2023, occurred in those who were too young to be fully protected by infant vaccination. Only 2 of these 21 infants born after the introduction of the maternal programme had a mother who had been vaccinated during pregnancy. In both cases the vaccination was too close to delivery to confer optimal passive protection in the infant. Estimated vaccine effectiveness against death in infants with pertussis whose mothers had been vaccinated was very high at 97% (2) based on pertussis cases from 2013 to 2019.

No pertussis-related deaths were reported in older children, adolescents or adults in 2023. However, this assessment is provisional and may be updated as there can be delays to final confirmation of Office for National Statistics official cause of death (for example,  in the event that an inquest is called).

Childhood vaccination uptake

The national vaccination schedule recommends pertussis vaccination at 8, 12 and 16 weeks of age and a pre-school booster at 3 years and 4 months.

Vaccine coverage estimates for 2023, evaluated between October and December for DTaP/IPV/Hib/HepB immunisation across England, was 91.3% for 3 doses at 12 months of age and 83.2% for the booster dose by 5 years of age (3). Coverage estimates for DTaP/IPV/Hib at 12 months of age were slightly lower than the coverage estimates for October to December, 2022 when the proportion of children vaccinated at 12 months was 91.9%, and coverage estimates were also lower for the booster dose, reported at 85.2% for the same period (4).

The introduction of social distancing and population lock downs in response to the COVID-19 pandemic from late March 2020, when some of this cohort would have been scheduled for vaccination, may have contributed to the modest decrease seen in the booster dose coverage.

Maternal vaccination programme

The maternal pertussis immunisation programme (5, 6) introduced in response to the 2012 outbreak became permanent from June 2019 (7) based on evidence of disease impact, high effectiveness and safety (8, 9, 10, 11). Women should normally receive their whooping cough vaccine around the time of their mid-pregnancy scan (usually 20 weeks) but can receive it from 16 weeks (7). To provide optimal protection to the baby, the vaccine should be given before 32 weeks. Women can still have the vaccine later in pregnancy and those who miss maternal vaccination can receive it up to the time their infant receives their first vaccines at 8 weeks of age.

UKHSA reported that the proportion of mothers due to give birth in 2023 who had been immunised with a pertussis containing vaccine in pregnancy in England ranged from a monthly average of 57.4% (July) to 60.8% (January) compared to 2022 when monthly averages were higher, ranging from 59.5% (June) to 64.3% (January) (12).

Surveillance data in young infants following the introduction of the pertussis immunisation in pregnancy programme demonstrated sustained low incidence in this age group, with expected seasonal increases. COVID-19 control measures appear to have had an additional impact on these observed effects. However, following the withdrawal of COVID-19 containment measures, and increased social mixing, the number of cases began to increase from mid-2023. It is therefore even more important that women are offered pertussis vaccination in pregnancy (ideally between 20 and 32 weeks) to optimise protection for their babies from birth, and for infants to complete the vaccination schedule on time.

Supplementary data tables from 1994 to 2023 are available to download.

Figure 1. Total number of laboratory-confirmed pertussis cases per evaluation quarter in England, 2011 to 2023

Figure 2. Incidence of laboratory confirmed pertussis cases by age group in England: 1998 to 2023

Table 1. Laboratory confirmed cases of pertussis by quarter and test method in England: 2023 [note 1]

Quarter	Culture	PCR	Serology	Oral fluid only	Total
January to March	1	4	23	1	29
April to June	6	42	45	13	106
July to September	15	76	119	57	267
October to December	15	65	250	124	454
Total	37	187	437	195	856

Table 2. Age distribution of laboratory confirmed cases of pertussis by test method in England: 2023 [note 1]

Age group	Culture	PCR	Serology	Oral fluid only	Total
Less than 3 months	14	33	1	0	48
3 to 5 months	4	19	0	0	23
6 to 11 months	3	21	1	0	25
1 to 4 years	4	35	5	8	52
5 to 9 years	1	14	13	50	78
10 to 14 years	1	21	64	91	177
15 years and over	10	44	353	46	453
Total	37	187	437	195	856

Note 1: Culture-confirmed cases may additionally have tested positive by any other method; PCR-confirmed cases may have additionally tested positive by serology or OF; and serology-confirmed cases may also have been confirmed by OF. Cases are only represented once in the table. Submission of all presumptive B. pertussis isolates is encouraged for confirmation of identity and to allow further characterisation for epidemiological purposes.

References

1. Office for National Statistics, 2023 population estimates

2. Amirthalingam G, and others (2023). Optimization of timing of maternal pertussis immunization from 6 years of post-implementation surveillance data in England. Clinical Infectious Diseases

3. Quarterly vaccination coverage statistics for children aged up to 5 years in the UK (COVER programme): October to December 2023. Health Protection Report volume 18 number 3, 26 March 2024

4. Quarterly vaccination coverage statistics for children aged up to 5 years in the UK (COVER programme): October to December 2022. Health Protection Report volume 17 number 3, 28 March 2023

5. Confirmed pertussis in England and Wales continues to increase. Health Protection Report volume 6 number 15, 13 April 2012

6. Department of Health (2012). ‘Pregnant women to be offered whooping cough vaccine’ (website news story, 28 September)

7. Joint Committee on Vaccination and Immunisation (2014). Minute of the meeting on 4 June 2014

8. Amirthalingam G and others (2014). Effectiveness of maternal pertussis vaccination in England: an observational study. The Lancet

9. Dabrera G, and others (2014). A case-control study to estimate the effectiveness of maternal pertussis vaccination in protecting newborn infants in England and Wales, 2012 to 2013. Clinical Infectious Diseases

10. Donegan K, and others (2014). Safety of pertussis vaccination in pregnant women in UK: observational study. British Medical Journal

11. Amirthalingam G and others (2016) Sustained effectiveness of the maternal pertussis immunization program in England 3 years following introduction, Clinical Infectious Diseases

12. Pertussis vaccination programme for pregnant women update: vaccine coverage in England, October to December 2023. Health Protection Report volume 18 number 3, 4 April 2024