COVID-19Infectious DiseasesPreventive Medicine


Why can’t today’s viruses play fair? Why can’t viruses like SARS-CoV-2 behave like the viruses of old—the varicella-zoster virus or the mumps virus? By that I mean, when you become ill with COVID-19 disease, why can’t you develop “permanent” immunity? I had mumps, measles, and chicken pox as a child. I was never vaccinated for these diseases because I had them long before vaccines existed. But because I had those diseases I will never get them again. The diseases produce adequate levels of antibodies that protect me from getting the disease for the rest of my life. I know this is true because in over forty years of medical practice I was exposed to chicken pox, mumps, and measles many times without becoming ill. 

As of now, COVID-19 seems to be different. We don’t yet know if COVID-19 will produce permanent natural immunity like chicken pox or if it will behave like influenza and require an annual revaccination against the anticipated strain for that season. It’s simply too early to tell. COVID-19 hasn’t been around long enough to have long-term antibody studies to answer the question. It will be many years before scientists know, but what we currently know is very encouraging. There is some good news!

It has been established that a large percentage of people who were sick with COVID-19, and recovered, have antibody levels that are adequate to prevent re-infection for several months. According to the CDC website, this has been proven many times. The staff and residents of “two British nursing homes” who tested positive for COVID-19 antibodies were 96% less likely to become infected during a second outbreak four months later. Another British study found an 84% reduction in re-infection over a seven-month period. A large U.S. study found a “90% reduction among persons with antibodies compared to persons without antibodies.” And antibody positive “U.S. military recruits had an 82% reduction in the incidence of COVID-19 infection over a 6-week period.” That means if you’ve had COVID-19 infection, you have only a 4%-18% chance of getting it again for up to seven months. It is hoped that the duration may increase over time.

The CDC’s statement reads “these findings….suggest that SARS-CoV-2 infection and development of antibodies can result in some level of protection against SARS-CoV-2 reinfection. The extent and duration of protection have yet to be determined. While life-long immunity has not been observed with…coronaviruses, studies of persons infected with SARS-CoV-1 and Middle East Respiratory Syndrome (MERS-CoV) coronavirus demonstrated measurable antibody for 18-24 months following infection, and neutralizing antibody was present for 34 months…” That is encouraging news!

This COVID-19 virus is a real pain, though! It has the audacity to mutate and cause people to get sick from a new version of the virus. Mumps, measles, and chicken pox didn’t do that. So, just when you think, well, I’ve had COVID-19 so maybe I can’t get it again, along come alpha, beta, gamma, and delta variants that also cause illness. And scientists think there are “thousands of others.” That’s very worrisome. We don’t know if they will cause more severe illness, if they will be as widespread, or if current vaccines will be effective in preventing them. The unknowns continue to confront scientists with more problems.  

I am encouraged by the optimism expressed by the CDC. For them to say “the presence of antibodies following infection offers some level of protection from reinfection….for 3 months or longer…and correlates with reduced incidence of infection,” is good news. They also report that patients with antibodies have an “80%-90% reduction in (the) incidence (of disease) for at least 6 months after infection.” 

Dr. G’s Opinion: This is all great news and is very encouraging. Natural immunity exists after acute illness, but for how long has not been determined. Vaccination produces adequate antibody levels as well, but, again, we don’t know for how long. As long as these variant strains don’t get a foothold, it may be possible to get ahead of the pandemic. Also, if more people get vaccinated, herd immunity can be obtained, and the disease will gradually become less significant. No one knows for sure when this will happen, or even if it’s a possibility. But if we all get vaccinated, I think the goal is attainable. 



Jiang XL, et al. Lasting antibody and T-cell responses to SARS-CoV-2 in COVID-19 patients three months after infection. Nat Commun 2021 Feb 9;12:897.

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