Customize your JAMA Network experience by selecting one or more topics from the list below.
How much protection against future infections does prior infection with SARS-CoV-2 infection provide? This is an important question for advising individual patients, as well as for projecting future outbreaks of SARS-CoV-2.
In this issue of JAMA Internal Medicine, Vitale and colleagues1 use the results of diagnostic reverse-transcriptase–polymerase chain reaction tests in Lombardy, Italy, to compare the incidence of SARS-CoV-2 infection among persons with prior SARS-CoV-2 infection with persons who tested negative for the virus.
The differences were dramatic. The incidence density per 100 000 person days was 1.0 (95%, CI 0.5-1.5) for persons with a history of infection and 15.1 (95% CI, 14.5-15.7) for persons without a history of infection. These results complement those of Harvey and colleagues2 from the US, who found that patients with a positive diagnostic nucleic acid amplification test result for antibodies to SARS-CoV-2 were much less likely to develop SARS-CoV-2 infection at 90 days than persons without antibodies.
Before assuming that people with documented SARS-CoV-2 infections, whether by polymerase chain reaction diagnostic testing or by presence of antibodies, are protected against future infections, there are 2 caveats. First, we do not know how long natural immunity lasts. Second, we do not know if natural immunity to the wild-type virus is equally protective for SARS-CoV-2 variants (viruses with genetic variations). As has been indicated by Spellberg and colleagues,3 achieving herd immunity through natural infection is a long and painful process, and, historically, the only human disease to be eradicated, smallpox, was eradicated through vaccination, not natural infection.
Because it is likely that immunization plus history of natural infection is better protection than natural infection alone, all persons should be encouraged to get vaccinated even if they have been previously infected with SARS-CoV-2. Although unproven, it is possible that vaccination provides broader immunity to variants than natural infection. And because we do not know how long vaccine protection will last or whether there will be variants that escape protection from vaccination, we may need immunization boosters and or reformulated vaccinations in the future.
Published Online: May 28, 2021. doi:10.1001/jamainternmed.2021.2966
Corresponding Author: Mitchell H. Katz, MD, NYC Health and Hospitals, 125 Worth St, Room 514, New York, NY 10013 (email@example.com).
Conflict of Interest Disclosures: None reported.
Identify all potential conflicts of interest that might be relevant to your comment.
Conflicts of interest comprise financial interests, activities, and relationships within the past 3 years including but not limited to employment, affiliation, grants or funding, consultancies, honoraria or payment, speaker's bureaus, stock ownership or options, expert testimony, royalties, donation of medical equipment, or patents planned, pending, or issued.
Err on the side of full disclosure.
If you have no conflicts of interest, check "No potential conflicts of interest" in the box below. The information will be posted with your response.
Not all submitted comments are published. Please see our commenting policy for details.
Katz MH. Protection Because of Prior SARS-CoV-2 Infection. JAMA Intern Med. 2021;181(10):1409. doi:10.1001/jamainternmed.2021.2966
Coronavirus Resource Center