Having repeated annual influenza vaccination can prevent natural immunity to the virus. It also can potentially increase the susceptibility to influenza illness in the event of a pandemic, or when the vaccine does not "match" the virus circulating in the community.
But now, researchers at the Influenza Center in Bergen have published an important study, which concludes that annual influenza vaccination does not increase susceptibility to influenza infection in years of vaccine mismatch
‘Annual vaccination of the influenza vaccine improves the first line defense though it has a very poor impact on the second line defense.’
These findings are important because they show that it is only positive to have annual influenza vaccination, and it supports continuing the policy of repeated annual vaccination, says Professor Rebecca Cox, Head of the Influenza Centre.
A better first line defence
Researchers at the Influenza Centre in Bergen have over a period of five years followed 250 healthcare workers. They were vaccinated in 2009 and had the annual vaccination in all subsequent seasons or no further vaccination between 2010 and 2013. 3000 blood samples were collected.
The results showed that both healthcare workers who had the annual vaccination, and those who did not get annually vaccinated, had the same second line defense, but those who had gotten annual vaccines had a better first line defense. The group that had annual vaccination, had not been prevented from developing natural immunity.
Important for the risk groups
Almost 1,5 million people in Norway have an increased risk of influenza complications. The influenza vaccine is annually updated to adapt to the rapid virus evolution. It is the only vaccine that is recommended on annual basis.
- For people in the risk groups, influenza could lead to pneumonia and exacerbation of chronic underlying diseases. Influenza can result in hospitalization, in the elderly this may lead to institutionalization, and in the worst case death. That is why it is so important that we can continue to recommend annual vaccination, especially now we know that it does not prevent natural infection, says Cox.
- Influenza vaccines have been in use for over 50 years, but there are very few studies that have been able to follow the same people for a long period of time particularly in such a well-documented group of vaccines.