Safety of MF59-adjuvanted A/H1N1 influenza vaccine in pregnancy: a comparative cohort study

Review on the effects of influenza vaccination during pregnancy on preterm births

“…36,41 Heikkinen et al conducted a mixed prospective and retrospective cohort study that evaluated the safety of MF-59 adjuvanted A/H1N1pdm09 vaccine among 2,295 vaccinated and 2,213 non-vaccinated pregnant women. 42 In this study a significant reduction in prematurity was seen in the vaccinated cohort in an analysis using proportional hazard models with gestational age as the time factor, whereas, when aOR was estimated using logistic regression models a similar however non-significant association between vaccination and preterm births was detected. 42 Preterm birth analyses after vaccination with seasonal IIV formulations containing pandemic strain Four studies in North America during and following the A/ H1N1 2009 pandemic assessed whether preterm birth rates differed between mothers who received seasonal influenza vaccine containing the pandemic strain and non-vaccinated women 37,39,46,47 (Table 2).…”

“…10,29,31,34,36,37,41,42,45,46,48 However, only 4 studies report on the effect of vaccination on prematurity stratified by trimester of pregnancy, 34,37,41,46 with one study suggesting a nonspecific protective effect of influenza vaccination on the rate of preterm births in women vaccinated during the third trimester. 41 The association of vaccine effect with the presence of influenza in the community is an important question to consider, as the most plausible direct biological mechanism of the vaccine effect on birth outcomes is likely through protection of maternal infection.…”

“…Six studies 10,27,31,36,42,48 including 3 large studies in Scandinavia found no significant association with A/H1N1pdm09 vaccination during pregnancy and preterm births. 10,31,36 Also in the study by Fell et al, in Canada where 21,363 women reported to have received only an A/H1N1pdm09 monovalent vaccination and 1,977 received both an A/H1N1pdm09 and a seasonal IIV during pregnancy in 2009/10, the prematurity rates did not differ between the vaccinated and the non-vaccinated groups after adjusting for maternal age, education, neighborhood, chronic hypertension, pregnancy-induced hypertension, preeclampsia, history of preterm birth and maternal smoking.…”

“…30,37,38,40,43,48 The A/H1N1 MF56-adjuvanted formulation was evaluated in Argentina, Italy and the Netherlands. 27,29,42 Four studies in Scandinavia described the birth outcomes after vaccination with an AS03-adjuvanted influenza vaccine. 10,31,36,41 In Germany and Ireland more than one vaccine formulation was commercially available and recommended for use in the pandemic campaigns.…”

“…To adjust for group differences and reduce confounding bias in observational studies 2 main approaches were used: propensity scores 31,34,37 and multiple logistic regression analysis. 10,21,27,29,30,33,35,36,39,[41][42][43][44][45][46][47][48][49] In propensity score analyses probability of vaccination is estimated as a function of available variables and then that score is used as a single matching covariate. The propensity score matching allows comparing the risks after vaccination between cohorts that had the same likelihood of being vaccinated.…”