Does a Previous COVID-19 Infection Make Me Immune?

Over recent weeks COVID-19 booster shots have been authorized for certain at-risk groups. The roll-out of booster shots has sparked discussion over how long antibody and immunity levels provided by the vaccines last, and whether vaccination is necessary if a person has previously contracted COVID-19. 

An Israeli retrospective study of medical records, that is yet to to be peer reviewed, indicated that people who had previous SARS-CoV-2 infections were less likely to get infected with COVID-19 and develop symptoms compared to people who have never been infected and who were vaccinated. This study was limited in its scope and not based on a prospective investigation that tests all study participants, tracks new infections and symptomatic infections, hospitalizations, and deaths that go forward in time. Scientific data from other studies are clear in that vaccines provide strong protection against severe illness, hospitalization, and death. According to a study published in Nature, vaccination increases the protection of natural immunity by enhancing immune response and providing stronger protection against different variants, including delta. 

Furthermore, people who received at least one dose of the Pfizer-BioNTech messenger RNA (mRNA) vaccine are also less likely to be reinfected compared to those who had COVID and remain unvaccinated. This point is critical since it is not clear for how long natural immunity can last. A study published in The Lancet Microbe indicates that reinfection can happen between 3 to 61 months after being infected with COVID-19, which is less than half the duration that the endemic coronaviruses circulating among humans have. In light of this research, Dr. Ajay Sethi, associate professor of population health sciences at the University of Wisconsin-Madison, commented that “the study underscores the importance for the public to understand that immunity from natural infection is not as long lasting as some may perceive, and certainly not lifelong.” In addition, according to Dr. Alexander Edwards, associate professor in biomedical technology at the University of Reading in the U.K., it is not yet clear that the chances of hospitalization or death are reduced when a person that previously contracted the virus is later reinfected. 

Being unvaccinated after having COVID-19 still poses a risk. The Kansas City Star reported the death of a man who was unvaccinated and who thought he was immune because he already had had the virus. “A family member being hospitalized with COVID is a harsh reminder to get vaccinated,” the stepmother of the man wrote on Facebook after he died. The doctors at the University of Kansas Health System recommend that those who were infected with the original strain of the virus and the more contagious Delta variant should get vaccinated. 

Age is also a factor in the efficacy of natural immunity. According to a Danish study, people who are under 65 years of age have 80% protection from natural immunity for at least six months, while those over 65 only have 45%. Commenting on the findings of this study, two professors from Imperial College London, Rosemary Boyton and Daniel Altmann, concluded that, “the hope of protective immunity through natural infections might not be within our reach and a global vaccination programme with high efficacy vaccines is the enduring solution.”

CDC data indicated that unvaccinated individuals in Kentucky “are more than twice as likely to be reinfected with COVID-19 than those who were fully vaccinated after initially contracting the virus.” CDC director Dr. Rochelle Walensky has urged those who have already been infected with COVID-19 to get vaccinated. “Getting the vaccine is the best way to protect yourself and others around you, especially as the more contagious delta variant spreads around the country,” she concluded. 


AM LLC is currently working nationwide with multiple states and public health agencies on testing, contact tracing, and vaccination programs. Counties, states, or K-12 partners that are interested in partnering with AM for COVID-19 mitigation support should contact Dr. Christopher K Orlea at

Related Posts