Background
During the 2009 influenza pandemic, pregnant women were at particular risk of serious influenza illness. This concern was further complicated by questions about vaccine safety in pregnant women raised by anecdotal reports of fetal deaths following vaccination.
Methods
We explored the safety of influenza vaccination of pregnant women by linking Norwegian national registries and medical consultation data to determine influenza diagnosis, vaccination status, birth outcomes, and background information for pregnant women before, during, and after the pandemic. We used Cox regression models to estimate hazard ratios of fetal death, with gestational day as the time metric and vaccination and pandemic exposure as time-dependent exposure variables.
Results
There were 117,347 eligible pregnancies in Norway in 2009–2010. Fetal mortality was 4.9/1000. 54% of pregnant women in their second or third trimester during the pandemic were vaccinated. Vaccination in pregnancy substantially reduced the risk of influenza diagnosis (adjusted hazard ratio, 0.30; 95% confidence interval [CI], 0.25 to 0.34). A clinical diagnosis of influenza in the mother increased the risk of fetal death (adjusted hazard ratio, 1.91; 95% CI, 1.07 to 3.41). Among pregnant women, the risk of fetal death was lower with vaccination, although this reduction was not statistically significant (adjusted hazard ratio, 0.88; 95% CI, 0.66 to 1.17).
Conclusions
Pandemic influenza in pregnancy was associated with increased risk of fetal death. Vaccination during pregnancy reduced the risk of influenza diagnosis. Vaccination itself did not increase fetal mortality, and may have reduced the risk of influenza-related fetal death during the pandemic.
MenBvac and MeNZB are safe and efficacious vaccines against serogroup B meningococcal disease. MenBvac is prepared from a B:15:P1.7,16 meningococcal strain (strain 44/76), and MeNZB is prepared from a B:4:P1.7-2,4 strain (strain NZ98/254). At 6-week intervals, healthy adults received three doses of MenBvac (25 g), MeNZB (25 g), or the MenBvac and MeNZB (doses of 12.5 g of each vaccine) vaccines combined, followed by a booster 1 year later. Two-thirds of the subjects who received a monovalent vaccine in the primary schedule received the other monovalent vaccine as a booster dose. The immune responses to the combined vaccine were of the same magnitude as the homologous responses to each individual vaccine observed. At 6 weeks after the third dose, 77% and 87% of the subjects in the combined vaccine group achieved serum bactericidal titers of >4 against strains 44/76 and NZ98/254, respectively, and 97% and 93% of the subjects achieved a fourfold or greater increase in opsonophagocytic activity against strains 44/76 and NZ98/254, respectively. For both strains, a trend of higher responses after the booster dose was observed in all groups receiving at least one dose of the respective strain-specific vaccine. Local and systemic reactions were common in all vaccine groups. Most reactions were mild or moderate in intensity, and there were no vaccine-related serious adverse events. The safety profile of the combined vaccine was not different from those of the separate monovalent vaccines. In conclusion, use of either of the single vaccines or the combination of MenBvac and MeNZB may have a considerable impact on the serogroup B meningococcal disease situation in many countries.
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