Going, Going, . . .

Two of my college age grandchildren just cannot seem to get Covid. No, I do not mean the vaccine, but rather I am referring to the actual virus. You might think that is a good thing, but au contraire, it is not. Each has been in very close quarters on numerous occasions with friends and roommates who have tested positive for the virus. Keep in mind that their individual risk from Covid is extremely low, and each time they are exposed to someone with the virus, the result is that each one is in quarantine for two weeks. I have lost track of how many times each of them has been quarantined for two weeks  . . . in two different states. Repeated Covid tests (for the 21 year old, seven separate Covid tests) – all negative.

They have both gotten antibody tested, and both are negative, and according to present knowledge, this means that they have not been previously infected. How can this be especially with a virus that is supposed to be very infectious? Is it possible that an individual could have been infected with Covid, and not be antibody positive?

A recent article from the Wall Street Journal by Dr. Marty Makary addresses this issue as well as the recent plummeting of Covid cases.

(Dr. Makary is a professor at the Johns Hopkins School of Medicine and Bloomberg School of Public Health.)

Why the recent dramatic drop in the number of cases? This decrease is occurring despite a number of things which would make one think that the opposite should be occurring. It is still winter, and in many parts of the country people are continuing to spend a lot of time indoors, as opposed to being outdoors where transmission is less. In addition in many parts of the country businesses are starting to open. Restaurants are opening. (Twice in the last two weeks I have eaten indoors at a restaurant.) Beauty Salons and barbershops are again seeing customers. Mask wearing and social distancing remain in vogue without any recent apparent change. From my personal unscientific observation there has not been any decrease in the number of people frequenting Costco or Walmart.

This significant decrease in the number of cases should not be happening . . . but yet it is! Why?

From Dr. Makary’s WSJ article:

“The consistent and rapid decline in daily cases since Jan. 8 can be explained only by natural immunity. Behavior didn’t suddenly improve over the holidays; Americans traveled more over Christmas than they had since March. Vaccines also don’t explain the steep decline in January. Vaccination rates were low and they take weeks to kick in.”

Dr. Makary questions, “Could the reason for the recent dramatic decrease in the number of new infections be because we are approaching herd immunity.”

Herd immunity! How can that be? 

The various estimates on the number needed to achieve herd immunity range from 60-80%, and certainly we cannot be close to that number with the relatively low percent of positive antibody tests. Even adding in the the 15% of Americans have received the vaccine, no way can we be close to the number needed for herd immunity, can we? Could antibody studies underestimate natural immunity. Antibody testing doesn’t capture antigen-specific T-cells, which develop “memory” once they are activated by the virus. (Survivors of the 1918 Spanish flu were found in 2008—90 years later—to have memory cells still able to produce neutralizing antibodies.)

Researchers at Sweden’s Karolinska Institute found that the percentage of people mounting a T-cell response after mild or asymptomatic Covid-19 infection consistently exceeded the percentage with detectable antibodies. T-cell immunity was even present in people who were exposed to infected family members but never developed symptoms. A group of U.K. scientists in September pointed out that the medical community may be under-appreciating the prevalence of immunity from activated T-cells.

Dr. Makary feels there is reason to think the country is racing toward an extremely low level of infection. As more people have been infected, most of whom have mild or no symptoms, there are fewer Americans left to be infected . . . in other words, herd immunity.

Dr. Makary’s hypothesis about under appreciated T-cell responses could explain my granddaughters’ apparent inability to get Covid. In each of their situations, perhaps a T-cell response to an original mild or asymptomatic infection and then an antigen-specific memory T-cell response to further exposures to Covid could explain their apparent inability to actually get positive Covid tests despite recurrent close-encounter exposures and negative antibody tests.

For a variety of reasons I hope that Dr. Makary is correct because that would mean that the Covid pandemic could be going, going, and soon gone.