Pregnant women receiving flu vaccine are not at increased risk of having a miscarriage, according to a new study.
Members of the Centers for Disease Control and Prevention’s (CDC’s) Advisory Committee on Immunization Practices (ACIP) discussed the findings Wednesday in addition to flu vaccine effectiveness and changes to Japanese encephalitis (JE) vaccine recommendations.
The study on flu vaccine and miscarriage was a matched case-control study of women ages 18-44 in the 2012-’13, 2013-’14 and 2014-’15 seasons.
Results showed no link between flu vaccine during pregnancy and spontaneous abortion within 28 days.
“The findings of the study then support current recommendations for vaccination for pregnant women in any stage of pregnancy,” said James Donahue Ph.D., D.V.M., M.P.H., senior epidemiologist with the Marshfield Clinic Research Institute who presented the data.
The study follows two previous studies. One found an association between the vaccine and spontaneous abortion among women who had been vaccinated in the previous season. Another study found no association. Dr. Donahue said the new study was a larger study and had a better design than the previous studies.
Flu vaccine effectiveness
This season, flu vaccines have been 47% effective for the general population and 61% effective for children, according to interim data from the CDC.
It did not have data specifically for live attenuated influenza vaccine (LAIV) and did not expect to in the coming months.
The CDC reintroduced a newly-formulated LAIV for 2018-’19 after pulling it for the previous two influenza seasons due to poor effectiveness, especially during H1N1 seasons. While the CDC did not express a preference between vaccine types this season, the AAP recommended using inactivated influenza vaccine as the primary vaccine choice. LAIV may be used for children who would not otherwise receive a vaccine. Both the CDC and AAP recommend everyone 6 months and older get vaccinated.
ACIP will discuss its recommendations for 2019-’20 when it meets again in June. The AAP typically releases its full influenza recommendations in September but hopes to be able to issue them earlier this year.
“There is no new U.S. LAIV effectiveness data for the current 2018-2019 season,” said Yvonne A. Maldonado, M.D., FAAP, chair of the AAP Committee on Infectious Diseases. “AAP will consider the existing data regarding LAIV effectiveness in determining its recommendations for the 2019-2020 season.”
Flu vaccine virus selection delay
Recently, the World Health Organization selected flu viruses for next season’s vaccines. However, it delayed a selection on influenza A (H3N2) until March 21 to collect more data.
A representative of the Food and Drug Administration (FDA) said the group’s advisory committee meets next week to discuss U.S. vaccines but also may delay selection for H3N2. He could not comment on whether that would impact manufacturing/availability.
Japanese encephalitis vaccine
ACIP also decided Wednesday to strengthen its recommendation for a Japanese encephalitis (JE) booster dose and to include children in this guidance.
It was one of several changes made to vaccine recommendations to protect against JE, which is transmitted by mosquitoes and most commonly seen in Asia and parts of the western Pacific.
JE vaccine Ixiaro was licensed in the U.S. in 1992 and has since been approved for everyone 2 months and older. While extremely rare for U.S. travelers, the disease can be severe. Travelers’ risk is higher in rural areas or during longer trips.
ACIP made small changes to its recommendations on vaccination to say JE vaccine is recommended for people moving to or traveling frequently or long-term to a country where JE is endemic. It should be considered for short-term travelers with increased risk based on when and where they are traveling and their activities. The vaccine is not recommended for travelers at very low risk.
The committee also strengthened language on booster doses to say they should (instead of may) be given at least a year after the primary series if the person is experiencing ongoing exposure or re-exposure to the virus. It also said this recommendation would apply to children as well as adults.
This recommendation follows a randomized trial among 300 children ages 14 months to 17 years in the Philippines. The study showed among those receiving a booster dose, 100% were seroprotected both at 28 days and two years after the booster dose.
In another vote, the committee approved an accelerated primary JE vaccine schedule for adults ages 18-65 of two doses on days 0 and 7-28.
If the CDC director approves ACIP’s recommendation, it will be published as an official recommendation in the Morbidity and Mortality Weekly Report.
Copyright © 2019 American Academy of Pediatrics
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