The media is reporting that immunity to CoV-2 disappears in a few months. This is based on a pre-publication report from researchers at King’s College in London that shows that of >90 infected patients, only 17% maintained significant levels of anti-CoV-2 antibodies after three months. The antibody response to the virus decays pretty quickly after the virus is cleared from an infected person’s body. The implication is that we quickly lose immunity to the virus.
However, this is a good example of how poorly the media sometimes reports on medical science matters.
In every infection that generates antibodies, the antibody level always decays pretty quickly after the infection runs its course. And thank goodness for that because your blood serum could be overloaded with protein if you kept pumping out antibodies to everything you were ever exposed to. Most readers of this blog have had numerous vaccinations in their youth and remain immune to most of the pathogens they were vaccinated against or exposed to. You don’t keep producing antibodies to all those pathogens throughout your life, but you still remain immune to those pathogens. How does that happen?
Antibodies are just one arm of your immune response to an infection. Antibodies are produced by blood cells called lymphocytes, specifically bone marrow derived lymphocytes, or B cells. When you are first infected with a pathogen, it takes some time for the B cells to be informed that there is an invader, but they gradually begin producing antibodies to that bug. Once the bug is eliminated, the B cells cool off and go into a dormant mode.
There also is another type of lymphocyte called T cells because they originate in the thymus, a gland in your neck. They come in different forms. There are cytotoxic T cells which recognize virally infected cells and kill them. There also are T cells, called helper cells, that encourage B cells and cytotoxic T cells to attack the invader. All of these go dormant after the infection is over. However, a type of T cell, called a memory cell, arises during the infection and floats in your blood as a sentinel guarding, often for many years, against future infection.
Memory cells, not antibodies are the basis of vaccination and immunity. If you are subsequently exposed to the same pathogen, memory cells sound an alarm that immediately mobilizes your dormant B cells and cytotoxic T cells to provide a quick response to an infection with a previously experienced pathogen.
So, the media articles implying that immunity to CoV-2 is short lived because the antibody response decays after three months are misleading. The fact of antibody decay does not mean that you are losing immunity. You are also developing memory cells while the B cells that produce antibodies are going into sleep mode.