Study finds how children born in October are least likely to get influenza

LOS ANGELES: According to a US study, children born in October are more likely to be vaccinated against influenza and less likely to be diagnosed with the disease than children born in other months. The results of the study were published in The BMJ.

According to the findings, the birth month is associated with both the timing of flu vaccination and the likelihood of a flu diagnosis, with October being the best time for young children to receive a flu shot, in accordance with existing recommendations. Annual influenza vaccine is especially critical for young children, who are more likely to have the flu and develop a serious condition that requires hospitalisation. Vaccination is advised in September or October to boost immunity during peak flu season.

Among young children in the United States, preventive care visits tend to occur during birth months and are a convenient time to receive the influenza vaccine, but large-scale studies of the optimal timing of vaccination are unavailable. To address this, researchers set out to assess the optimal timing of influenza vaccination in young children.

Using health insurance claims data, they identified over 800,000 children aged 2-5 years who received an influenza vaccination between August 1 and January 31 during 2011-18. They then analysed rates of diagnosed influenza among these children by birth month. After accounting for a range of potentially influential factors such as age, sex, existing conditions, healthcare use and family size, the results show that October was the most common month for children to be vaccinated.

Children born in October also had the lowest rate of influenza diagnosis. For example, among children born in August, the average rate of influenza diagnosis across flu seasons studied was 3% compared with 2.7% for children born in October and 2.9 per cent for those born in December.

This is an observational study and the authors acknowledge that their findings are limited to insured children who received medical care. Nor can they rule out the possibility that other unmeasured factors may have influenced their results.

Nevertheless, results were similar after additional analyses to evaluate whether the relation between birth month and influenza risk was due to chance, providing greater confidence in their conclusions. "Our findings suggest that US public health interventions focused on vaccination of young children in October may yield the best protection in typical flu seasons," they said. "The study's findings are consistent with current recommendations promoting October vaccination," they added.