The CDC’s U.S. Flu Vaccine Effectiveness Network Investigators published a preprint finding that recurrent yearly influenza shots increase influenza infection risk.
The preprint authors asked if vaccination timing and prior influenza infections affected repeat vaccines’ risk of infection.
They found that these factors “cannot fully explain the increased infection risk in repeat vaccines compared with non-repeat vaccines.”
Patients with acute respiratory illnesses at one of the specified clinics were monitored for eight seasons from 2011 to 2019. Over 55,000 clinical visits were assessed for vaccination status. Repeat vaccines had a 10% higher risk of developing influenza type A H3N2 than non-repeat vaccines, but not influenza type B or H1N1.
If the present subtype was the same, previous influenza patients were more protected.
The authors found that neither factor significantly changed the estimates on the effects of repeat vaccination, even though repeat vaccines got vaccinated about a week earlier than non-repeat vaccines and unvaccinated who became infected during the prior season got vaccinated the following season.
You can read the study at this LINK
