Whooping cough vaccine in pregnancy was introduced in the UK in 2012, after an outbreak was declared, to protect infants against whooping cough from birth. Young babies are at highest risk of severe disease, needing hospital care and, rarely, dying if they catch whooping cough. Scientists at the UK Health security Agency (UKHSA) have looked before at how well vaccine in pregnancy can protect babies against the disease. This has shown very high protection against whooping cough disease, hospital admission and death in babies whose mothers were vaccinated. Disease levels have been very low in England following the use of measures to control COVID-19 between April 2020-July 2021 but rose quickly after November 2023 across the country in all age groups, including babies. This study will look at the most recent whooping cough cases in babies and young children to compare the vaccine status of their mothers with that of women living nearby who gave birth at a similar stage of pregnancy, in the same month and who were a similar age. From this we can estimate how effectively vaccinating in pregnancy can protect young babies against whooping cough over a recent time. We can also look at whether babies whose mothers were vaccinated in pregnancy respond as well as babies whose mothers were not vaccinated when they receive their own baby vaccines. This work is important so that we can continue to monitor how well the vaccine programme is working and keep this under review in case anything changes.
Our aim is to estimate the vaccine effectiveness (VE) of maternal pertussis immunisation against laboratory confirmed pertussis in infants using the case-cohort (screening) method. We will estimate the coverage of maternal pertussis vaccine in pregnant women (defined using the pregnancy register) with a live infant born from 1st January 2020 onwards in CPRD Aurum data.
In order to estimate VE, estimates of coverage by month of birth, mother’s age, and geographic region from the CPRD data will be carried forward to use with separate UKHSA laboratory confirmed case data. The aggregated estimates of coverage will be matched to the separate case data on these covariates, and VE will be calculated using the screening method.
Our main objective is to estimate VE against lab confirmed pertussis in those <3 months old (prior to infant scheduled to receive their own vaccinations against pertussis). We will also estimate VE against hospitalisation, and against death.
Exposure in the CPRD Aurum data is maternal pertussis vaccination . The separate UKHSA pertussis case data are the outcome group with the same covariates recorded as the CPRD data.
In response to the increasing laboratory confirmed cases of pertussis being observed across England and 5 pertussis infant deaths reported in the first three months of 2024, UKHSA established a national incident to co-ordinate the response to minimise severe disease and death in infants, at highest risk of disease.
Vaccination remains the key intervention in preventing further severe infant disease, particularly in the first months of life, through the vaccination in pregnancy programme. This has previously been demonstrated to be highly effective in preventing severe infant disease and death, using CPRD data. In light of the increasing pertussis activity including infant deaths, it’s critical to be able to rapidly update current estimates of vaccine effectiveness from the maternal programme.
Coverage of pertussis vaccination in women with a live birth according to mother’s age, gestational age (or weeks prior to delivery) at time of vaccination, month of birth and geographic region. This, in combination with UKHSA data on the vaccination status of the mothers of infants with laboratory confirmed pertussis will enable estimation of vaccine effectiveness using the case-cohort (screening) method.
Gayatri Amirthalingam - Chief Investigator - UK Health Security Agency (UKHSA)
Jemma Walker - Corresponding Applicant - UK Health Security Agency (UKHSA)
Anna Mensah - Collaborator - UK Health Security Agency (UKHSA)
Emma Heymer - Collaborator - UK Health Security Agency (UKHSA)
Helen Campbell - Collaborator - UK Health Security Agency (UKHSA)
Julia Stowe - Collaborator - UK Health Security Agency (UKHSA)
Nick Andrews - Collaborator - UK Health Security Agency (UKHSA)
Sonia Ribeiro - Collaborator - UK Health Security Agency (UKHSA)
CPRD Aurum Pregnancy Register