Study prompts call to ex­am­ine flu vac­cine link to mis­car­riage

Re­search fo­cuses only on in­ci­dents in first 19 weeks of preg­nancy

Packet & Times (Orillia) - - LIFE - MIKE STOBBE A nurse prac­ti­tioner pre­pares a flu vac­ci­na­tion in Rockville, Md.

NEW YORK — A puz­zling study of U.S. preg­nan­cies found that women who had mis­car­riages be­tween 2010 and 2012 were more likely to have had back-to­back an­nual flu shots that in­cluded pro­tec­tion against swine flu.

Vac­cine ex­perts think the re­sults may re­flect the older age and other mis­car­riage risks for the women, and not the flu shots. Health of­fi­cials say there is no rea­son to change the gov­ern­ment rec­om­men­da­tion that all preg­nant women be vac­ci­nated against the flu. They say the flu it­self is a much greater dan­ger to women and their fe­tuses.

The Cen­ters for Dis­ease Con­trol and Preven­tion has reached out to a doc­tor’s group, the Amer­i­can Con­gress of Ob­ste­tri­cians and Gyne­col­o­gists, to warn them the study is com­ing out and help them pre­pare for a po­ten­tial wave of worry from ex­pec­tant moms, CDC of­fi­cials said.

“I want the CDC and re­searchers to con­tinue to in­ves­ti­gate this,” said Dr. Laura Ri­ley, a Bos­ton-based ob­ste­tri­cian who leads a com­mit­tee on ma­ter­nal im­mu­niza­tion. “But as an ad­vo­cate for preg­nant women, what I hope doesn’t hap­pen is that peo­ple panic and stop get­ting vac­ci­nated.”

Past stud­ies have found flu vac­cines are safe dur­ing preg­nancy, though there’s been lit­tle re­search on im­pact of flu vac­ci­na­tions given in the first three months of preg­nancy.

This study fo­cused only on mis­car­riages, which oc­cur in the first 19 weeks of preg­nancy and are com­mon. As many as half of preg­nan­cies end in mis­car­riage, ac­cord­ing to a March of Dimes estimate that tries to in­clude in­stances in which the mis­car­riage oc­curs be­fore a women even re­al­izes she was preg­nant.

Flu and its com­pli­ca­tions kill thou­sands of Amer­i­cans every year. The el­derly, young chil­dren and preg­nant women are es­pe­cially at risk. When a new “swine flu” strain emerged in 2009, it killed 56 U.S. preg­nant women that year, ac­cord­ing to the CDC.

The study’s au­thors, two of whom are CDC re­searchers, saw a big dif­fer­ence when they looked at women who had mis­car­ried within 28 days of get­ting a shot that in­cluded pro­tec­tion against swine flu, but it was only when the women also had had a flu shot the pre­vi­ous sea­son.

They found 17 of 485 mis­car­riages they stud­ied in­volved women whose vac­ci­na­tions fol­lowed that pat­tern. Just four of a com­pa­ra­ble 485 healthy preg­nan­cies in­volved women who were vac­ci­nated that way.

The first group also had more women who were at higher risk for mis­car­riage, like older moms and smok­ers and those with di­a­betes. The re­searchers tried to make sta­tis­ti­cal ad­just­ments to level out some of those dif­fer­ences but some re­searchers don’t think they com­pletely suc­ceeded.

Other ex­perts said they don’t be­lieve a shot made from killed flu virus could trig­ger an im­mune sys­tem re­sponse se­vere enough to prompt a mis­car­riage. And the au­thors said they couldn’t rule out the pos­si­bil­ity that ex­po­sure to swine flu it­self was a fac­tor in some mis­car­riages.

Two other medical jour­nals re­jected the ar­ti­cle be­fore a third, Vac­cine, ac­cepted it. Dr. Gregory Poland, Vac­cine’s edi­tor-in-chief, said it was a well-de­signed study that raised a ques­tion that shouldn’t be ig­nored. But he doesn’t be­lieve flu shots caused the mis­car­riages. “Not at all,” said Poland, who also is di­rec­tor of vac­cine re­search at the Mayo Clinic.

Though this study may cause worry and con­fu­sion, it is ev­i­dence “of just how rig­or­ous and prin­ci­pled our vac­cine safety mon­i­tor­ing sys­tem is,” said Ja­son Schwartz, a Yale Uni­ver­sity vac­cine pol­icy expert.

Some of the same re­searchers are work­ing on a larger study look­ing at more re­cent data to see if a pos­si­ble link be­tween swine flu vac­cine and mis­car­riage holds up, said James Don­ahue, a study au­thor from the Wis­con­sin-based Marsh­field Clinic Re­search In­sti­tute. The re­sults aren’t ex­pected un­til next year at the ear­li­est, he said.


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