Immunity after COVID-19 will wane

Dear Dr. Roach: In your column about the COVID-19 vaccine, you review the Pfizer vaccine results. You say: “People with a history of COVID-19 infection benefitted from the vaccine just as much as those without, suggesting no natural immunity was present.” I’m curious what results from the study led you to this conclusion. Thank you!

Anon.

Answer: There is some degree of immunity after natural COVID-19 infection, for at least the first three months after infection. After that, immunity begins to wane.

In the large study for the Pfizer vaccine, longer-term immunity was evaluated by comparing the risk of acquiring COVID-19 between those who had antibodies showing previous infection against those who did not. The “attack rate” was 1.3% in people with and without COVID-19 antibodies at baseline. The placebo group attack rate from enrollment to the end of the study was 1.3% both for participants without evidence of prior infection at enrollment and for participants with evidence of prior infection at enrollment. These data do suggest that previously infected individuals can be at risk of COVID-19 (i.e., reinfection) and could benefit from vaccination.

Dear Dr. Roach: My son contracted encephalitis at age 7 months in 1963, which left him deaf and with expressive aphasia. We never understood what happened.

I recently read an article about a correlation between herpes simplex and encephalitis. My husband had many episodes of cold sores. We wonder if that could have been the source of infection. It could be a warning to other parents not to let people kiss their babies. What do you think?

M.

Answer: There are many causes of encephalitis. While herpes simplex viruses are a common cause, there are many viruses, bacteria and even parasites and fungi that could have been the cause.

I wouldn’t advise parents in general to avoid kissing their children; however, it’s a good idea not to do so when a parent is having an outbreak or oral herpes (cold sores).

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