1 Summary

• From 01 January 2024 to 21 April, 675 clinically suspected pertussis cases have been notified to the Public Health Agency.
• Of those notified during 2024 to 21 April, 527 were laboratory confirmed.

2 Background

Pertussis (also known as “whooping cough”) is a highly contagious but vaccine preventable bacterial respiratory disease that is usually caused by Bordetella pertussis. It is normally characterised by a “whooping” cough, cold and fever. For more information about pertussis, please visit NI Direct | Pertussis. Pertussis typically follows a cyclical pattern with epidemics occurring every three to five years. For more information about previous years’ reports, please visit PHA | Annual VPD Reports.

A vaccine against pertussis, which also provides protection against diphtheria, tetanus, polio, Haemophilus influenzae type b (Hib) and hepatitis B (DTap/IPV/Hib/HepB vaccine) is included in the Northern Ireland childhood vaccination schedule at age two, three, and four months. A further booster against pertussis (also protecting against diphtheria, tetanus and polio) is provided three years after the primary course and before school entry. Vaccination against pertussis can also be offered prenatally (to pregnant women) ideally from 16 weeks up to 32 weeks pregnant.

For more information on the childhood immunisation programme, please visit NI Direct | Childhood immunisation programme and for further information on pertussis vaccination for pregnant women, please visit NI Direct | Whooping cough vaccination for pregnant women.

Details of case definitions and methods are at the end of this document. Data were correct at 21 April 2024.

3 Pertussis notifications, 2019-2024

The number of notified clinically suspected pertussis cases from the start of 2019 until the report date are shown (Table 3.1).

Please note: in the table above data for 2024 is up to 21 April

3.1 Trends

Pertussis notifications in Northern Ireland have continued to increase since January 2024 (Figure 3.1 and Figure 3.2). The increases noted during February and March are partly attributable to increase awareness. The reduced number of cases in week commencing 01 April 2024 are likely attributable to the Easter holidays. There have been 527 laboratory confirmed pertussis cases reported in 2024 to date, more than the 182 reported in 2019.

The supplementary table below shows counts of pertussis notifications recorded by week.

Figure 3.1: Incidence of pertussis notifications, by week of notification, all ages, 2023 - 2024.

Figure 3.2: Incidence of pertussis notifications, by month of notification, all ages, 2019 - 2024.

Please note: in the figure above the most recent month is incomplete

4 Discussion

There have been 527 laboratory confirmed pertussis cases during 2024. There has been an increase in notifications of clinically suspected and confirmed pertussis since January 2024. Similar increases have been reported in multiple countries across Europe. The number of pertussis cases reported during 2020 to 2023 had been particularly low, a secondary impact of interventions to control the spread of COVID-19.

Pertussis vaccine coverage has reduced in Northern Ireland during recent years; NI PHA | Vaccination coverage. Increasing coverage of pertussis vaccination, both prenatal and in childhood, is crucial to ensure widespread protection and keep cases of pertussis low.

5 Methods

Pertussis notifications are reported by clinicians to the Public Health Agency and were extracted from the case management database. Pertussis is notifiable in Northern Ireland under the Public Health Act (1967) Northern Ireland.

Cases are presented by the date that they were recorded on the PHA database. Notified cases will be removed from future reports if PHA is notified that clinical investigations later result in an alternative diagnosis. Numbers may therefore reduce.

Data were processed using R.

6 Supplementary Table