By Dr. Anthony Policastro

A few months ago, I wrote an article on delayed immunity. The term for that is anamnestic response. Antibodies represent immediate immunity.

At that time most people were not talking about antibodies from COVID immunization. That is now the case. So a refresher appeared to make sense.

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 had measurable antibody levels.

They were then given an additional dose of the vaccine and checked. 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.

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, 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, all the talk about how long vaccine antibodies last is mainly just talk. We will not know how well the vaccine works from just measuring antibodies. Anamnestic response is important.

COVID-19 Update

The number of new cases nationally was just at 500,000 for the past week. That represents about a 10 percent increase over the previous three weeks.

While the numbers are higher, it does not really qualify as a surge. Locally Sussex County numbers remained pretty steady. There were 288 new cases for the week.

Fully immunized individuals nationally has gone from 18 percent to 22 percent of the population in the last week. Delaware has gone from 18 percent to 21 percent as well.

The number of first doses nationally has moved from 32 percent of the population to 36 percent. Delaware has moved from 34 percent to 38 percent.

Those increases are all higher than they were the previous week.

One of the hot topics in COVID-19 immunization is that of vaccine passports. On March 31st the New England Journal of Medicine had an editorial on the topic. It listed both pros and cons.

The title was: “Vaccine Passport” Certification – Policy and Ethical Considerations. Anyone who has strong personal feelings one way or the other should read the editorial to see the vantage points of both sides.

Early on I had spoken about Coronavac vaccine. It was made the traditional way. It made sense that it would be the best vaccine for that reason. However, recent studies have shown that it does not reach the 95 percent effectiveness of the mRNA vaccines. Thus I stand corrected on that count.

The FDA has asked for a pause in the Johnson and Johnson vaccine. It is related to six episodes of something called a cavernous sinus thrombosis (blood clot in a brain sinus).

It comes after 6.8 million doses of the vaccine were administered. Thus its incidence is less than 1 in a million.

All cases occurred in women between the ages of 18 and 48. All occurred 6 to 13 days after the immunization. All were associated with low blood platelets.

You might remember that back in 2015 I had an episode of low blood platelets (blood clotting cells) after a pneumonia.

The cause of that was the antibodies to the pneumonia thought my platelets were pneumonia cells.

In this case the antibodies to the vaccine think that the platelets are COVID-19 virus. It is what is called an autoimmune reaction.