In recent times, the increasing prevalence of swine flu and novel vaccine technologies are some of the major drivers for the global H1N1 vaccines market. Swedish researchers report that the vaccine against the H1N1 "swine flu" strain of influenza doesn't seem to have a link to birth defects.
"Research has shown conflicting risk estimates for congenital malformation in pregnant women receiving Pandemrix in the first trimester, with odds ratios (ORs) ranging from 0.67 to 2.18," Jonas F. Ludvigsson, MD, PhD, of the Karolinska Institutet in Stockholm, and colleagues wrote. Although several studies have attempted to adjust for confounding factors, none has studied siblings discordant for vaccination exposure, which, by design, would control for familial confounding (genetic and shared early environmental factors).
‘Vaccination for H1N1 influenza during pregnancy is likely unrelated to congenital malformations in exposed offspring.’
Ludvigsson and colleagues performed a prospective, population-based study of offspring born between Oct. 1, 2009 and Oct. 1, 2011 to mothers who received the monovalent AS03-adjuvanted H1N1 influenza vaccine (Pandemrix) during pregnancy. They evaluated the risk for offspring malformation, taking into account familial factors.
One obstetrician who reviewed the research said the findings should ease concerns women might have about the vaccine. "This year's flu vaccine includes protection against an H1N1-like virus," noted Dr. Jennifer Wu, an ob/gyn with Lenox Hill Hospital in New York City.
She pointed out that the H1N1 strain made headlines in 2009-2010 as "swine flu" reached pandemic levels in the United States. But the new Swedish study "indicates that first trimester administration of H1N1 vaccine does not seem to increase congenital birth defects," Wu said.
Ludvigsson's team found no sign that maternal vaccination boosted the overall risk of birth defects in babies.
Current recommendations from the U.S. Centers for Disease Control and Prevention advise all pregnant women to receive a seasonal flu vaccine since they are especially vulnerable to complications from influenza.