Flu shot early in season offers better protection for pregnant women

May 19, 2011

Vaccinating pregnant women against influenza early in the flu season improves protection for them and their infants, a new study suggests.

Vaccinating pregnant women against influenza early in the flu season improves protection for them and their infants, a new study suggests.

Researchers at Duke University used a mathematical model to estimate the effects of influenza vaccination at different points in the flu season. They found that benefits-especially prevention of illness in infants, who can’t be vaccinated before 6 months of age-decrease if vaccination is postponed past November. Only those infants whose mothers were vaccinated within the first 4 weeks of vaccine availability experienced significant protection. Vaccination later in the season prevented fewer doctor visits and hospitalizations among pregnant women than earlier vaccination.

“The greatest population benefit from seasonal influenza vaccination in pregnancy is realized if pregnant women are vaccinated as soon as possible after seasonal TIV [trivalent inactivated vaccine] becomes available. Efforts to increase vaccine rates should be concentrated early in the influenza season,” the authors conclude.

They estimate that vaccinating all pregnant women would reduce the number of flu-related hospitalizations during pregnancy by more than one third, to 1,235 annually, and would decrease the number of doctor visits from more than 54,000 per year to about 23,000. In addition, hospitalizations of infants younger than 6 months of age could be reduced from more than 4,700 per year to slightly more than 3,000.

Fewer than 40% of pregnant women in the US receive a flu vaccination each year, notes lead author, Evan R Myers, MD.

The Centers for Disease Control and Prevention recommends that vaccination begin in September or as soon as the current year’s vaccine is available. Flu season in the United States can extend from October to May; it usually peaks between January and March.

The study, funded by GlaxoSmithKline Inc, was published onlineApril 18 in the American Journal of Obstetrics and Gynecology.