Repeat Influenza Vaccination Linked to Higher Risk of Infection: CDC Preprint

Scientists still have questions about the mechanism involved in the increased infection risk among repeat vaccinees.

By Marina Zhang

12/29/2023

Updated:

12/29/2023

 

A recent preprint co-authored by the U.S. Centers for Disease Control and Prevention’s (CDC) U.S. Flu Vaccine Effectiveness Network Investigators finds that repeat annual influenza vaccines are associated with an increased risk of influenza infection.

The preprint authors initially wondered if vaccination timing and influenza infections in prior seasons may have contributed to repeat vaccinees’ increased risk of infection.

However, they concluded these factors “cannot fully explain the increased infection risk in repeat vaccinees compared with non-repeat vaccinees.”

Repeat Vaccinees More Likely to Contract 1 Type of Flu

The study followed patients who had presented themselves with respiratory diseases at one of the designated clinics between the 2011 and 2019 seasons. Over 55,000 clinical visits were analyzed, and vaccine status was further examined.

Repeat vaccinees, when compared against non-repeat vaccinees, had a 10 percent increased risk of contracting the influenza type A H3N2 virus but not for influenza type B and influenza type A H1N1 variants.

Those who contracted influenza in prior seasons were more protected against infection if the current circulating variant was of the same subtype.

While repeat vaccinees tended to get vaccinated around a week earlier than non-repeat vaccinees, and the unvaccinated who became infected the prior season did tend to get vaccinated the following season, the authors found that neither factor significantly changed the estimates on the effects of repeat vaccination.

An Ongoing Dilemma

Increased risk of influenza infection among the repeat vaccinated is a phenomenon commonly observed for decades.

 

For audio the source is https://www.theepochtimes.com/health/repeat-influenza-vaccination-linked-to-higher-risk-of-infection-cdc-preprint-5555230?src_src=News&src_cmp=breaking-2023-12-30-2&est=aU3FGeHOdoyfbCWyD7JAeH6IGp2rznPm5glDwHWQ9U5%2BxbcXhUaDmPhLGw%3D%3D