The Department of Epidemiology at the University of Groningen, Netherlands lead by Edwin Van den Heuvel, has conducted a massive review of already published studies to find that the seasonal flu shots are effective for seniors over 60 during outbreaks and epidemics. The new review was published in The Lancet Infectious Diseases.
The most vulnerable people are those in the age groups of under 2 and over 60, who are already sick with another disease. The case-control studies followed the test-negative design, which scientists say is the best, because it rules out bias due to misclassification of infection.
The test-negative design means that the researchers only reviewed studies that compared older people with similar health care-seeking behavior. Let’s say someone doesn’t really like going to the doctor, and because of that they are also less likely to have a flu shot, than a person who visits their doctor regularly. Including the first type of people in the review would produce biased results that would make the vaccine more effective than it is.
Dr. Michael L. Jackson, who also took part in the review, explained that people who are old and sick are less able to do to the doctor’s and are also more likely to have complications if they do come down with the flu. Comparing them to healthier people who get the flu shot is going to give the vaccine more credit than it deserves.
The reviewers found and analyzed a total of 35 studies from Europe, the U.S. and Australia, that matched their inclusion criteria.
The analysis showed that during flu season, people over the age of 60 who received shots were up to 57% less likely than those who didn’t get vaccinated to test positive for a flu infection. The same analysis of the studies revealed that the seasonal flu shots were more effective during widespread and regional outbreaks, than during local virus activity.
Dr. Jackson stated on the review that concluded flu shots are effective for seniors:
This reinforces what we already know, the vaccine works modestly well for seniors. […] Efforts should be renewed worldwide to further increase uptake of the influenza vaccine in the elderly population.