Skip navigation
× You have 2 more free articles available this month. Subscribe today.

Pandemic Medical Update: “Herd Immunity” at Prisons?

Course of the Pandemic

Declining numbers of infections, hospitalizations and deaths: After the peak in mid-January at about 220,00 cases per day, infections have been declining in the United States. In mid-March, infections appeared to be stabilizing at about 60,000 per day, a level similar to the peak last summer. This is still a very active and dangerous pandemic.

But people are feeling good because the numbers are trending down and more than 2 million people are being vaccinated every day. States such as Texas and Florida have terminated their mask mandates and re-opened restaurants, bars, theaters and stadiums. Public health authorities are warning, again, that this relaxation of controls is premature and could result in another surge of infections. With the new variants in circulation that spread more easily and rapidly, this could be a tragic mistake, again. The same thing happened last fall when various secular and religious holidays brought large numbers of people together indoors to celebrate, followed by a substantial surge in infections.

Spread in gyms: Recent studies in gyms in Chicago and Honolulu demonstrated spread of coronavirus in gyms during intense workouts. This should come as no surprise, as rapid, deep breathing generates infectious aerosols that can be inhaled by others in the same room. For those who still go to gyms during the pandemic, preventive measures such as masks, keeping distant from others, limited numbers of people indoors at the same time, and increased ventilation may help reduce the risks. Of course people with diagnosed COVID-19, those recently exposed to it or with symptoms of illness, must not go to the gym at all.

“Herd Immunity” in California prisons? “Herd immunity” is an idea in epidemiology that occurs when so many people in a population have gotten sick or become immune that disease transmission slows or ceases. It is believed that this starts to occur when about 70% of the population is immune.

On March 9, 2021 the Sacramento Bee newspaper reported its review of COVID-19 infection data from the California Department of Correction and Rehabilitation (CDCR). There was a surge of infections in CDCR facilities during and after the winter holidays. As a result of this surge, the review found that in seven prisons more than 70% of the prisoner population had been infected with COVID-19. An additional six prisons have had more than 60% infected. Vaccination of older prisoners and those with medical conditions that make them higher risk for severe disease also will contribute to the population immunity.

On the one hand, it is shocking that 70% of the population was subjected to infection. That is the result of substantial failure of prevention efforts in the prisons and among the guards who enter the prison from the community daily. On the other hand, it means that transmission may be interrupted in those facilities. Those prisons may no longer serve as a reservoir of disease that can spread out to the local community from the guards or to other prisons following prisoner transfers. Even when herd immunity has occurred, ongoing testing of people with symptoms, isolation of cases, identification of close contacts of each case, and quarantine of contacts are critically important measures to maintain control of the disease.


Johnson & Johnson vaccine is available: The vaccine produced by Johnson & Johnson was authorized for emergency use in the United States last month. It was shown to be highly effective at preventing symptomatic disease, hospitalization, and death from COVID-19. This vaccine has some advantages over the other two in use in the U.S. (Pfizer and Moderna). It is effective with only one injection, and does not require extreme low temperatures for storage. This makes it easier to store, ship, and administer in point-of-care sites such as medical offices, pharmacies, community health centers as well as prisons and jails. Also, pop-up immunization sites in community centers, houses of worship and large residential complexes will be more easily accomplished with this vaccine.

Pfizer vaccine prevents asymptomatic infections, too: The original studies to prove vaccine effectiveness looked only at whether the vaccine prevented disease with symptoms.Analysis of new data from Israel has shown that the Pfizer vaccine is also highly effective at preventing infection without symptoms. This is very important news, because it means that the vaccination not only prevents hospitalization and deaths, but also will reduce overall disease transmission, too. We hoped for this, but it had not yet been demonstrated to be true.

New Coronavirus Variants

Pfizer vaccine effective against B.1.1.7:The coronavirus variant known as B.1.1.7 was first identified in the United Kingdom (UK). It is more infectious and therefore spreads more rapidly in a susceptible population. Widespread disease due to B.1.1.7 flared up in England, Ireland (last fall) and more recently in Italy. Studies of immunity after vaccination in Israel, where B.1.1.7 is widespread, showed that the Pfizer vaccine also is highly effective against B.1.1.7.

Epidemic P1 in Brazil: The coronavirus variant known as P1 has spread widely in Brazil. Major outbreaks of disease in every city and region have overwhelmed the hospitals with critically ill patients. Evidence is emerging about the characteristics of this variant. It is much more infectious, causing illness in virtually all household contacts. It also appears to be so different from the original pandemic coronavirus strain that some people who already had COVID-19 earlier during the pandemic are getting sick again with P1. We don’t know yet if the current vaccines will protect us from P1. Current vaccines may be partially effective, or perhaps ineffective. Even weakly effective vaccine immunity is better than no resistance at all.

The emergence of a variant that is both more infectious and able to infect people who already had COVID-19 is very bad news. As it spreads around the world it could give new energy to the pandemic, causing widespread illness and death all over again, perhaps even worse than earlier waves of infection.

Staying Safe

Ventilation of indoor spaces: With widespread planning to re-open public schools for in-person learning there has been more attention to ventilation of indoor spaces to prevent spread of COVID-19. An article in the New York Times on March 17, 2021 examined the effect of different levels of ventilation on models of spread of infectious aerosols in a typical indoor public school classroom. The models assumed that students wore masks and were spaced at least 6 feet apart.

The models looked at the effect of no ventilation, one open window, and one open window with a fan blowing in and an air cleaner installed in the classroom. They modeled the density and circulation of infectious aerosols when one infected student was introduced into the classroom.

They found that with no ventilation, 5% of the air students were breathing had recently been exhaled by another student. As expected, the more fresh air coming into the room through the open window, the less dense the aerosols that could infect other students in the room. The article also pointed out that adding a second open window with a fan blowing out would have been even better.

Stay out of populated indoor spaces if you can. If you must go inside with others, try to insist on improved ventilation with open windows and fans blowing both in and out. This will improve the safety for everyone in the room.

Safe practices for people who are fully vaccinated: In March, the Centers for Disease Control and Prevention (CDC) issued guidelines for safe practices for people who have been fully vaccinated against COVID-19. First, it recommended that everyone, even those fully vaccinated, continue safe practices in public places: wear masks, stay apart, avoid crowds and avoid poorly ventilated indoor spaces. Fully vaccinated people can meet socially indoors with others who are fully vaccinated without masks. Additional recommendations for mixing unmasked with unvaccinated people from a single household and quarantining after exposure also were provided but have little relevance in the prison setting. Fully vaccinated prisoners still have to quarantine for 14 days after exposure to a COVID-19 case, according to these new CDC guidelines.


There is reason for optimism because cases and deaths are declining and immunizations are proceeding rapidly. President Biden expects there will be enough vaccine by the end of May to immunize the entire U.S. population. So, by May, vaccines should be available to anyone who wants one. On the other hand, the P1 variant poses a significant risk for a newly aggressive pandemic. Continued vigilance is needed. Stay safe! 


Michael Cohen was the medical director for the New York state juvenile justice system for 20 years and previously provided medical care for incarcerated adults at the New York City Rikers Island jail and at Greene CF in Coxsackie, New York. For 10 years, he participated in a support group for people with diabetes at Great Meadow CF in Comstock, New York. With the group, he co-authored the Prisoner Diabetes Handbook published by Southern Poverty Law Center and distributed by Prison Legal News. Heal the sick. Raise the fallen. Free the prisoners.

As a digital subscriber to Prison Legal News, you can access full text and downloads for this and other premium content.

Subscribe today

Already a subscriber? Login