Immunization Science

Influenza Vaccine During Pregnancy and Infant Hospitalizations

This matched control study assessed whether influenza vaccination of pregnant women decreased hospitalization among their newborns.

The article

Influenza Vaccine Given to Pregnant Women Reduces Hospitalization Due to Influenza in Their Infants. Benowitz I, Esposito DB, Gracey KD, et al. 2010; Clinical Infectious Diseases 51: 1355-61. 

Explanatory note: Influenza is responsible for about 200,000 hospitalizations and 36,000 deaths in the United States every year. Those who are at the greatest risk are infants, pregnant women, the elderly, and those with chronic diseases. Among children, the highest risk is for children less than 12 months of age, especially those less than 6 months of age—for whom no effective vaccine is available. Influenza vaccination of women during pregnancy has been recommended to prevent illness in the mother as well as possibly to prevent influenza in her infant.

The question

Does influenza vaccination of pregnant women decrease hospitalization among their newborns?

The study

In this matched case-control study, all infants younger than 12 months of age hospitalized at Yale New Haven Children’s Hospital between October 2000 and April 2009, and who had influenza virus detected in their nose by direct fluorescent antibody tests, made up the study group. Each case was matched to one or two infants who were hospitalized at about the same time, were similar in age, but who had negative tests for influenza virus. A mother was considered immunized if the researchers could identify written documentation that she had had vaccination during pregnancy prior to 14 days before delivery.

The findings

The researchers found 157 cases of infants with influenza and 270 control infants whose family could be located and who agreed to participate. Children who had influenza were less likely than controls to live in families who had received influenza vaccine and their mothers were also less likely to have been immunized. The effectiveness of influenza immunization of expectant mothers for preventing hospitalization of their infants during the first six months of life was estimated to be 91.5%.

The relevance/bottom line

Influenza immunization of pregnant women is an effective strategy to prevent hospitalization of their newborn infants with influenza during the first 6 months of life.

NNii’s comment

Influenza immunization of pregnant women—as well as other household members—protects newborns and young infants from influenza.