Age matters, especially when it comes to vaccines. For those above 65, a new study shows that getting the flu shot in the morning provides better immunity against a strain of the influenza virus than getting the same shot in the afternoon.
For the study, researchers from the University of Birmingham in the UK recruited 276 pensioners and took their blood samples before they were given the vaccine. Half the group received the flu shot between 9am and 11am; the other half received it between 3pm and 5pm. The flu shot offered immunity against three common types of flu viruses.
A month later, when the researchers analyzed new blood samples from the participants, they found that the differences were huge. Those who received the shot in the morning had four times as many antibodies against H1N1 (swine flu strain), 50% more antibodies against B-strain flu, and about the same number of antibodies against H3N2, when compared to those who received the flu shot in the afternoon.
The results of the study were published in the journal Vaccine.
While both the groups produced enough antibodies against H1N1 and H3N2, only those receiving the morning shot produced enough antibodies against the B-strain. That means if those receiving the afternoon flu shot caught the B-strain flu, their immune system would succumb to the attack.
Older people have weaker immune systems, which puts them at a greater risk of dying from flu. According to one estimate, just changing the time of the day when pensioners receive their annual flu shot could save as many as 2,400 lives in the UK alone.
Researchers don’t yet know for sure why the timing of the day for the flu shot results in such different immune responses. A person’s immunity can be affected by many factors: diet, sleep, exercise, and, of course, the time of the day.
Some experts not involved in the study believe that the differences observed could just be a chance observation. They want to wait for larger trials to replicate the results before doctors and hospitals are advised to change their vaccination practices for older adults.
As for individual advice, the evidence is clear that getting the flu shot every year is good for you and for those around you. When you go to get that flu shot, it won’t hurt to get a morning appointment instead.