How long do antibodies last?

[JohnR41]

I remember reading about a test that was done a while back. Researchers wanted to see if anyone still had antibodies to a serious influenza outbreak that happened around 1917. They tested older people who were alive back at that time. And they did find people who still had antibodies to that virus.

But when I asked a few different nurses how long I would be protected by this years' flu shot, two of them said 3 months and one said a year. I don't understand why there should be so much conflicting information on this. Where are they getting the information that it only lasts 3 months?

[tjlhb]

No idea. However, different varieties of flu circulate every year, which is why last year's flu vaccine may not be protective against the common types of flu circulating this year.

[NCGuy]

In 1917 there was no vaccine so the people who are still around and survived the flu have natural antibodies they developed by being exposed to the flu. The flu vaccines that come out annually are for the specific strain that they believe will be the one circulating in the coming year. Each year the strains differ or change completely so a new vaccine is necessary. Usually the flu shot you get will give you immunity against those specific strains for 4-6 months.