The influenza virus

Influenza can be deadly!

I get a flu shot every year. In a good year, the flu shot will decrease my risk of catch­ing the flu by about 60%. In a bad year, it decreas­es my risk of catch­ing the flu by only about 20%. But even that seems like a good deal to me. I’d glad­ly get a jab in the arm for even a 20% decrease in the risk of a week or more of mis­ery. Also, I like the idea that my flu shot might make me less like­ly to make oth­er peo­ple sick. The flu shot is also remark­ably safe. Seri­ous side effects are extreme­ly rare. Mean­while, influen­za remains an impor­tant cause of hos­pi­tal­iza­tion and death.

The flu is not just a bad cold, it is an infec­tion with influen­za virus. Every year, hun­dreds of thou­sands of peo­ple around the world die as the result of the sea­son­al influen­za virus infec­tions. Since the influen­za virus mutates so rapid­ly, the vac­cine has to be updat­ed every year.

The influen­za vac­cines are far less effec­tive than the oth­er rec­om­mend­ed vac­cines. But it is against the vac­cine-pre­ventable dis­ease that you are most like­ly to encounter.  As a result, it is the vac­cine that is most like­ly to make a real dif­fer­ence for you per­son­al­ly. Even if the flu vac­cine pro­vides only a par­tial match to the strain of flu virus that you encounter, it can give you par­tial pro­tec­tion. Also, because of a process called affin­i­ty mat­u­ra­tion, even a par­tial match gives your body a head start at pro­duc­ing anti­bod­ies that will be effec­tive. So even if you catch the influen­za, your ill­ness might be short­er and milder.

It’s hard to tell whether your flu shot worked. That’s because there are many flu-like ill­ness­es besides influen­za going around. Also, the effec­tive­ness of the vac­cine varies from year to year. Yet when you look at the research, you can see that hav­ing a flu shot does reduce the risk of hos­pi­tal­iza­tion and death among the most vul­ner­a­ble peo­ple .

The flu vac­cine has to be updat­ed every year. That’s because the influen­za virus mutates so rapid­ly. For that rea­son, the World Health Orga­ni­za­tion runs an inter­na­tion­al pro­gram to mon­i­tor devel­op­ments in the influen­za virus­es, to help devel­op vac­cines against dan­ger­ous emerg­ing strains.

In 1918–1919, a par­tic­u­lar­ly dead­ly strain of flu spread around the world. This Great Pan­dem­ic killed more peo­ple than died in World War I. It killed more peo­ple in 25 months than HIV killed in 25 years. That is why epi­demi­ol­o­gists and virol­o­gists are par­tic­u­lar­ly afraid of dan­ger­ous new flu strains. The most dan­ger­ous strains are the ones that have recent­ly jumped from pigs or birds to human beings.

Pho­to by kat m research