Although most people recover from the flu on their own, certain groups are at increased risk of more serious illness. Studies have suggested that some flu infections during pregnancy can increase the risk of the pregnant woman dying, being hospitalized or giving birth too early. Infants aged 0-6 months who catch the flu also have a greater risk of being hospitalized compared to older children. Flu vaccination during pregnancy can lower these risks in both the mother and her baby. Since 2009, pregnant women in the UK have been offered the flu vaccine. However, many choose not to have it, partly because they are concerned about whether the vaccine is safe for their developing child – especially if it is received in early pregnancy
Overall, studies examining flu vaccine safety in pregnancy have not found evidence to suggest it is unsafe for the unborn child. However, additional studies on the safety of the flu vaccine during pregnancy (and early pregnancy in particular) can provide further reassurance to pregnant women and it is important to continue to monitor safety. Our study will examine flu vaccine given in pregnancy and will focus on birth defects, developmental disorders and miscarriage as outcomes of interest.
The 2009/10 influenza pandemic necessitated the production of a monovalent, inactivated H1N1 vaccine (PIIV) which was offered in 2009/10 to all pregnant women regardless of trimester. From 2010/11 onwards, all pregnant women have been offered the seasonal inactivated influenza vaccine (SIIV). This study will first use linked primary and secondary care data and death certificate data to develop diagnostic algorithms for the following outcomes: a) congenital malformations (diagnosed pre- or postnatally), b) pervasive developmental disorders and c) spontaneous abortion.
Using a cohort study design, we will then examine whether there is any association between SIIV administered at any point in pregnancy, or in individual pregnancy trimesters between 2010-2016, and major malformations, pervasive developmental disorders and spontaneous abortion. Secondary outcomes of interest following SIIV receipt in pregnancy will include assessing whether the infants/foetuses of pregnant women are at increased risk of developing major or minor malformations, malformations of particular organ systems (defined by EUROCAT) or spontaneous abortion in the 4 weeks after vaccination. Risks will be examined separately for women who received the 2009/10 PIIV. Finally, we will examine the prevalence of inadvertent vaccination and exposure to teratogenic drugs in order to provide information for the direction of future safety studies.
Sara Thomas - Chief Investigator - Not from an Organisation
Maria Peppa - Corresponding Applicant - London School of Hygiene & Tropical Medicine ( LSHTM )
Caroline Minassian - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )
Jemma Walker - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )
Nick Andrews - Collaborator - Public Health England
Punam Mangtani - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )
CPRD Mother-Baby Link;HES Admitted Patient Care;ONS Death Registration Data;Patient Level Index of Multiple Deprivation;Practice Level Index of Multiple Deprivation;Pregnancy Register