We enter the season of coughing and body aches and pains. And if you haven't been immunized yet, now might be the perfect time to get the flu.
Although influenza vaccine campaigns began back in August, several studies published in recent years show that the effectiveness of the flu vaccine actually diminishes over time in the months following the shot. So if you immunize too early, you may lose some – or all – of your immunity by the time of the flu season in January and February. (If you have already had flu, there is nothing you can do this season, but remember this advice the next time the flu turns.)
Vaccination a little later ̵
Why people who vaccinate too early may be more likely to get the flu
In a 2017 study, researchers from the Centers for Disease Control and Prevention looked at data from four recent seasons of the flu in the United States to track whether and when vaccine efficacy begins to decline
They found that stroke was most effective immediately after vaccination, followed by dropout, which varied slightly according to the type of influenza virus. (There are four types of influenza viruses – A, B, C and D – seasonal influenza is caused by influenza A and B. Different strains of these pathogens circulate each year.) So for influenza A (H3N2) and flu B, the effectiveness of the vaccine dropped by 7 percent a month after vaccination. In influenza A (H1N1), it dropped by 6 to 11 percent per month.
In general, researchers say, "We observed a decrease in influenza vaccine protection with an increase in the time after vaccination for influenza types / subtypes."
Another 2018 book examines even more flu seasons – seven – and finds similar pattern: In all seasons, every additional 28 days between vaccination and influenza testing are associated with an approximately 16 percent increase in the chances of testing positive for each flu. "This finding is predominantly due to the decrease in immunity against influenza A, the authors – most of whom are in Kaiser Permanente – writes.
Other recent documents have reached similar conclusions – such as a study in the UK for the influenza season 2011-2012 and a study from Spain that found a drop in the effectiveness of the vaccine to zero 119 days after vaccination.
"Although the root causes of intra-seasonal immunity are up for debate … the evidence of its existence is becoming increasingly difficult to ignore," writes a pair of researchers in the Journal of Clinical Infectious Diseases . The early bird gets the flu. They note that there is much more to understand about this phenomenon – how it differs between age groups or people with certain underlying diseases that affect the immune system, such as HIV.
But for the time being, the editors wrote: "The prospect that the vaccine administered in August loses its efficacy in only 3 or 4 months is worrying." This is because "millions of people who were vaccinated in August and September, may be at risk until January or February, historically when the flu season is at its peak.
And what does this mean for people who have already been vaccinated? You can't do much this year. The CDC says there is no benefit to vaccinating twice a season, and the Advisory Committee on Immunization Practices, which defines a vaccination policy in the US, has not yet changed its guidelines to reflect new research. They now recommend vaccination by the end of October and warned this year: "Vaccination early – for example, in July or August – can lead to reduced influenza protection later in the season, especially among the elderly."
Very Good Public Health Causes of Flu Vaccination
As previously reported, flu vaccines carry very little risk – and the great potential benefit of avoiding serious illness for you and the people around you. This is because getting the vaccine is not just about protecting yourself; it is about protecting others through herd immunity. When enough people are immunized, the virus spreads less. So even if you think you can get rid of the flu, you could spread it to the more vulnerable people who can't.
Older people, young children, pregnant women and people with compromised immune systems are particularly vulnerable to the flu. So herd immunity and vaccine are especially important for these groups. During the 2017-2018 flu season, 80 percent of childhood deaths occurred in unvaccinated children, according to the CDC.
As for the treatment of influenza, most people can simply wait for their illness at home, rest a lot and take care not to infect others. But people in these high-risk groups – young children, pregnant women, people over 65, those with other chronic illnesses – may want to seek medical help and antiviral medicines like Tamiflu immediately.
In the meantime, there are other, even simpler, things you can do to mitigate the risk of contracting the flu or spreading the virus to others. These include good old-fashioned hand washing, covering your mouth when you cough, and again, staying home if you are sick.