Influenza vaccination may reduce secondary infection spread amongst household contacts

1. Influenza vaccination was associated with a reduced risk of secondary influenza infections among household contacts, with an estimated effectiveness of 21%.

Evidence Rating Level: 2 (Good)

Influenza vaccinations are recommended for all individuals aged 6 months and older in the United States for the prevention of influenza infection. However, while the effectiveness of influenza vaccines in preventing serious disease and hospitalization has been investigated, the effectiveness of influenza vaccines in preventing any influenza infection regardless of symptoms as well as secondary infections has not been well characterized. This cohort study therefore sought to investigate the effectiveness of influenza vaccines in preventing secondary infections following influenza introduction into a household. Between 2017 and 2020, individuals with laboratory-confirmed influenza infection from Tennessee and Wisconsin were enrolled as primary cases if they were the first known person in their household to become ill. In total, 699 primary or co-primary cases (median[IQR] age, 13[7-38] years) and 1581 household contacts (median[IQR] age, 31[10-41] years) were included in the study. The estimated vaccine effectiveness (VE) of influenza vaccines in preventing laboratory-confirmed influenza infections among household contacts was 21.0% (95% CI, 1.4% to 36.7%). The estimated VE of influenza vaccines in preventing influenza B was 56.4% (95% CI, 30.1% to 72.8%), while no detectable VE was observed in preventing influenza A infection (5.0%; 95% CI, −22.3% to 26.3%). Overall, this study found that influenza vaccination was associated with a reduction in risk of influenza infection among household contacts of the vaccinated individual. However, this association existed only for influenza B infections and not for influenza A. 

Click to read the study in JAMA Network Open

Image: PD

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