Here’s your word for today: anamnestic

By Dr. Anthony Policastro

I like to write about and explain technical medical terms. In the past I have written about tachyphylaxis and technoference. This week’s word is anamnestic.

It refers to one of the forms of protection against infection. When we receive a vaccine we develop antibodies.

When we have an infection we develop antibodies.

After the infection the antibody levels can be measured. That is how we typically determine if people remain protected against the illness.

If antibodies are present, the patient is protected. Those antibodies are produced by one type of immune cell.

For example a study has looked at antibody levels in humans who have had hepatitis B vaccine in infancy.

At the 20-year point only 37 percent of them still have measurable antibody levels.

Another study has looked at rabies vaccine. The numbers were small since there are not many people who get rabies vaccine.

Their antibody levels after the vaccine were present in 98 percent of the individuals.

In both cases antibodies could be measured. For hepatitis B the number was pretty low. For rabies the number was pretty high.

The second part of the study was to give an additional dose of the vaccine and check the response. This was done to look at the function of the second group of immune cells in the body.

This group of cells does not put out antibodies on a regular basis. However, they have a memory for previous infections. In both hepatitis B and rabies, these cells proved their worth.

All patients, regardless of antibody levels, poured out a huge number of antibodies to the infection into the bloodstream within a matter of days. This pouring out of large amounts of antibodies is what is known as an anamnestic response. It is part of the body’s protective mechanism.

One of the questions being asked about COVID-19 is how long will the antibodies in the bloodstream actually last. This is true for the actual infection. This is true for the vaccine.

That is probably the wrong question. The right question is whether individuals who have been infected or receive vaccine will have an anamnestic response on subsequent exposure.

If the answer is yes, then the issue of measurable antibodies is significantly overblown. The individuals are clearly going to be protected.

Unfortunately, there is no way of knowing if that will be the case until well down the road.

However, in the interim, we need to be careful about vaccine recommendations based solely on antibody levels.

Just as they did with hepatitis B and rabies, they need to look at whether further exposure to COVID will create a protective anamnestic response.

Once we have the information, we will know a lot more about protection.

In the meantime, everyone can add the word anamnestic to their vocabulary.

They can also try learning to spell it. It is a real annoyance to have to type it on a computer.

Glad this article is finished so I can stop doing so.

2020-10-08T07:43:49-05:00 October 8th, 2020|HEALTH|