Spanish researchers have evaluated the risk of complications from influenza among pregnant and not pregnant women of reproductive age. The results suggest that flu jab could reduce the risk of admission to the ICU or fatal evolution in pregnant women who are hospitalized with influenza infection.
The risk of hospitalization with severe influenza infection increases eight times with pregnancy among women of reproductive age. This is one of the conclusions of a study conducted by Clara Mazagatos Ateca, a researcher at the Center for Biomedical Research in Network for Epidemiology and Public Health (CIBERESP) at the National Epidemiology Center of the Carlos III Health Institute, led by Amparo Larrauri.
For this work the researchers used information from the surveillance system of severe, hospitalized and confirmed cases of influenza in Spain (which is part of the Spanish Influenza Surveillance System) from the 2010-11 until 2015-16 seasons. The results have just been published in the journal PLOS ONE.
“In the study, the relative risk of hospitalization in pregnant women was calculated by comparing the rate of hospitalization [of woman] with confirmed influenza in this group with the rate of those not pregnant,” the researchers explained.
Pregnant women are one of the groups considered at higher risk for the development of serious episodes after influenza infection and the World Health Organization (WHO) includes them as a recommended group for influenza vaccination in any trimester of pregnancy.
Although reports on the benefit of the vaccine and its safety in pregnant women support the official recommendations for influenza immunization, providing new evidence on the risk of severe influenza and the protective role of the vaccine in pregnancy could contribute to improving vaccination coverage in this population’s group.
The results have shown that “in women of childbearing age hospitalized with influenza infection, the risk of complications increases with the presence of underlying pathologies such as morbid obesity, with the delay of more than 48h at the start of antiviral treatment or depending on the type of virus which causes the infection [greater complications with the virus A (H1N1) pdm09 compared to A (H3N2) or B].” However, Clara Mazagatos added, “we have not been able to demonstrate an association between pregnancy and increased risk of admission to the ICU or mortality in women of reproductive age hospitalized with influenza.”
Low coverage of the vaccine
When exploring the role of influenza vaccine in the prevention of severe episodes and fatal outcome in hospitalized pregnant women, the authors found that of the 167 pregnant women who were included in the study, only 5 (3.6%) had received the influenza vaccine.
This low coverage, which contrasts with the official vaccination recommendations, has not allowed a sufficient sample size to perform an adjusted analysis of the effect of the vaccine against serious complications of influenza. Despite this, the results suggest that the influenza vaccine could reduce the risk of admission to the ICU or fatal outcome in hospitalized pregnant women.
The findings of this study support national and international recommendations for influenza vaccination in pregnant women. Considering the high risk of hospitalization after influenza infection, pregnant women should be considered a risk group for severe influenza illness and could benefit from the administration of the seasonal influenza vaccine.