We are in the midst of a serious pandemic in which more than 34 million people have been infected and more than one million have already died worldwide. Before 2019, no human had been infected with the coronavirus SARS-CoV-2, that causes the disease called COVID-19. The pandemic is so extensive and deadly because this coronavirus is highly transmissible and all humans who are exposed to SARS-CoV-2 will become infected. The only way that the pandemic will end is when a sufficient percentage of people become immune to COVID-19, most by being vaccinated plus a lesser number of people who have been infected with the virus and recovered. This is called herd immunity. Researchers tell us that in the U.S., the pandemic will not end until about 70 to 90 percent of the population has some degree of immunity (JAMA, 2020;324(8):732). We do not know how long vaccinated people will be protected from getting COVID-19, but recent studies look very encouraging.
People Who Recover from COVID-19 Appear to Have Lasting Immunity
Scientists from the University of Arizona, College of Medicine -Tucson, followed more about 6000 people who developed COVID-19 infections and found that most were immune to that virus seven months after infection, because their blood contained two potent antibodies to protect them (Immunity, October 13, 2020). There are reports of people who were thought to have recovered from COVID-19 appearing to have been infected a second time, and there is one report in which a person died from his second infection. However, the authors of the Arizona study feel that most people who recover from COVID-19 may be protected against getting the disease again for a long time. Details of this study include:
• Viruses are not living units; they must get into cells to stay alive. If they cannot get into cells, they die very quickly. The coronavirus has a spike protein that is the key that lets it enter human cells. If that spike protein is damaged, the virus cannot get into human cells and it dies very quickly.
• About 14 days after you are infected with the coronavirus, your immune system’s plasma cells produce short-term IgM and IgA antibodies to attach to and kill the virus. Later your immune system produces long-term IgG antibodies that can last up to a lifetime against some viruses and can prevent you from getting a second infection.
• The authors developed a very accurate test to measure these long-term IgG antibodies against the regions that contain the spike protein that lets the virus enter human cells.
• Their research found that most people who recovered had high levels of long-term IgG antibodies against the spike protein regions of the coronavirus for at least five to seven months after infection, the time they collected their data to write this report. They believe that future data will show that these antibodies will last much longer than that.
• Several papers already show that long-lasting IgG antibodies against a similar virus called SARS-Cov-1 last at least 17 years, the longest that data has been collected so far.
• Of 5,882 tests completed in the Arizona study, there was only one false positive. The U.S. Food and Drug Administration granted emergency use authorization for this test in August 2020.
Reaching Herd Immunity with Vaccines
Herd immunity will not be achieved by waiting for everyone to become infected “naturally”; it will only occur when we have an effective vaccine for the virus. For example, polio recurred “naturally” every year in the United States for more than 40 years, from 1916 to the mid 1950s, until the Salk vaccine was developed and administered in more than 90 countries. Vaccines have controlled polio, smallpox, diphtheria, rubella, and many other infectious diseases. For some of these diseases, a single course of vaccination protects for a lifetime, while others such as influenza require more frequent vaccines.
For a graphic explanation of how herd immunity works, study this demonstration from the Washington Post. Run the simulations several times, and go all the way to the end to see how many deaths would occur if “natural” spread of COVID-19 were used to try to reach herd immunity, without vaccines. Note that herd immunity does not require that everyone get vaccinated. Only about 70-90 percent of the population needs to be immune, which will include both people who have been vaccinated and a smaller number of people who have been infected with the disease. Whether or not you get vaccinated will always be a personal decision.
Coping Until the Pandemic Ends
The COVID-19 pandemic will continue until we have herd immunity, which should occur within a few years after widespread distribution of an effective vaccine. We do not yet know how long a vaccine will protect a person, and whether vaccination will be needed just once or more often, as with yearly flu vaccines. Future studies will tell us how long the protection lasts, either from a vaccine or from having been infected.
Until vaccines become available, my rules to live by include:
• Wear a face mask any time you expect to be around people who are not members of your household
• Stay at least six feet away from other people
• Avoid anyone with respiratory symptoms
• Use 20-second soap hand washes frequently throughout the day
• Try not to touch your eyes, nose or mouth, the primary sources of viral entry into your body
• If you feel sick, stay home
• If you decide to travel, go by car if possible. Personally, I am avoiding group travel such as trains, planes, buses and ships.
• Spend lots of time outdoors. Transmission of the virus occurs most often in closed spaces, particularly crowded places with poor air circulation.