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According to a new study of four countries and six influenza seasons, influenza vaccination during pregnancy can reduce the risk of contracting a serious illness by 40% in a woman – enough to require hospitalization.
The findings, the first to specifically examine hospitalization, help answer a key question about the use of the vaccine during pregnancy and can help guide public health policies, particularly in income countries low or intermediate, according to a multinational team led by US researchers. Centers for Disease Control and Prevention (CDC) reported today in Clinical Infectious Diseases.
Pregnant women are at risk of influenza complications and the women's vaccination strategy during pregnancy is a research strategy aimed at protecting newborns who are too young to be vaccinated. The CDC estimates, however, that only about half of pregnant women are vaccinated against influenza, despite a strong safety record
Allison Naleway, Ph.D., co-author of the Kaiser Permanente Center for Health Research, said in a CDC press release that pregnant women face many threats to their health and that of their baby during pregnancy, including the flu. "The results of this study underscore the fact that there is a simple, but effective, way to reduce the risk of flu-related complications during pregnancy: get vaccinated against the flu."
Moderate protection, similar to other groups
The CDC and its partners analyzed health system registrations from 2010 to 2016, including integrated laboratory, medical and immunization records from Australia, Canada (Alberta and Ontario), Israel and the United States. United States (California, Oregon and Washington). The analysis includes 2 million pregnant women and over 80% of pregnancies straddling an influenza season, increasing the risk of women being exposed at some point in their pregnancy.
Using a negative test pattern, the researchers adjusted the site, season, calendar and medical conditions to high risk.
Of 19,450 hospitalizations for acute or febrile respiratory disease in a pregnant woman, only 1,030 were tested for influenza using the reverse transcriptase polymerase chain reaction test, considered the absolute reference. Influenza was detected in 58% of those tested. Overall, 13% of women who tested positive for influenza were vaccinated, compared to 22% of those who tested negative, for an overall vaccine efficacy of 40% (95% confidence interval, 12%). % to 59%), which corresponds to moderate protection.
The investigators wrote that the moderate protection they had found against hospitalization was similar to or slightly lower than that estimated for adults in general and about the same as that of a less severe flu. not requiring hospitalization in pregnant women. Their results were consistent during the start, peak and end periods of the influenza season and were similar for women with and without other high-risk medical conditions.
Mark Thompson, Ph.D., co-author of the study and epidemiologist for the CDC's influenza division, said in a statement: "Our study found that influenza vaccination works just as well for women regardless of the trimester and even reduced the risk of having flu during childbirth. "
Evidence of influenza vaccine protection against serious diseases in pregnant women could help low- and middle-income countries justify the cost of the vaccine, the team wrote. They added that their findings could help develop the use of the vaccine in high-income countries, since the use of influenza vaccine in pregnant women is well below national and international targets.
Control the confounding factors
In a related commentary in the same issue, Flor Munoz, MD, pediatric infectious disease specialist at Baylor College of Medicine in Houston, wrote that pregnant women and young babies are among the most vulnerable groups in the face of influenza epidemics and pandemics. She added that recommendations for vaccination of pregnant women had been evolving since 1957, when the Surgeon General had initially included them among the high-risk groups to be vaccinated.
She noted, however, that participation was low and that most low- and middle-income countries do not offer the vaccine to pregnant women.
The new study fills an important information gap, writes Munoz, noting that the strengths of this carefully designed study include a range of influenza seasons, geographical environments and sites where the flu vaccine was recommended without fresh for pregnant women. She added that negative test design helps reduce misclassification of cases and confusion with health-seeking behaviors.
In addition, she noted that the researchers had identified several other possible confounding factors, such as site, season, underlying medical conditions, trimester of pregnancy, admission to intensive care unit and the diagnosis of pneumonia.
"The PREVENT [Pregnancy Influenza Vaccine Effectiveness Network] This study provides reassuring evidence that influenza vaccination during pregnancy is effective in preventing hospitalization, a serious complication of influenza in pregnant women, and provides additional support to encourage the implementation of vaccination programs. Influenza kindergarten in the world.
See also:
October 11 Clin Infect Dis abstract
October 11 Clin Infect Dis comment
Press release of October 11 CDC
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