Study shows H3N2 vaccine protection drops sharply within 6 months
A new meta-analysis of 14 studies shows that vaccine effectiveness (VE) against influenza A H3N2 drops 33% within 6 months of immunization, while VE against influenza B declines by 19%. A small VE decline against influenza A H1N1 was not statistically significant.
The data offer guidance to countries planning the timing of flu shots: Countries with cooler climates see flu seasons that span 6 months, but year-round protection from the flu is required in temperate and tropical regions.
To conduct the study, the authors looked at VE data collected in Europe, the United States, Kenya, Thailand, and Australia. Flu seasons from 2009 to 2016 were included in the study.
The authors said there is still no way to calculate the rate of declining protection, but by 180 days after vaccine administration, protection against H3N2 drops significantly.
The authors suggest that multiple vaccination throughout the year may be a way to combat waning VE in some populations. "Vaccinating every six months in the tropics is attractive due to the simplicity, low cost, and safety profile of the standard dose inactivated vaccine."
Dec 6 J Infect Dis study
Maternal influenza vaccine offers protection for newborn
A study yesterday in the Journal of Infectious Diseases shows that prenatal maternal flu vaccination was associated with good protection against flu in infants. The research was based on data collected during the 2013-14 influenza season in Japan.
Researchers found that the flu vaccine administered during pregnancy was 61% effective in preventing influenza in infants, and postpartum maternal vaccination was 53% effective. Babies younger than 6 months of age are not recommended to receive the flu vaccine, and many countries, including the United States and Japan, routinely recommend that women get vaccinated during pregnancy.
The study was based on records from 117 hospitals in Osaka. A total of 3,441 infants were included in the study, 39% of whom had mothers who received the flu shot either during pregnancy or in the first 6 weeks postpartum. A total of 71 infants (2%) were diagnosed as having influenza during the study period. Maternal influenza was associated with a 36-fold increased risk of infant influenza.
"Pregnant women should receive influenza vaccination in order to protect not only themselves but also their infants. If they fail to receive influenza vaccination during pregnancy, postpartum vaccination would also be useful in protecting their infants from the threat of influenza," the authors concluded.
Dec 5 J Infect Dis study