If you’ve had COVID-19, one dose of vaccine may be as good as two: what could this mean for the global vaccination effort?
Identifying people who have recovered from COVID-19 could provide a way to accelerate protection of populations against the disease.
- 13 October 2021
- 4 min read
- by Linda Geddes
Many world leaders have stated strong support for the World Health Organization’s goal of vaccinating at least 70% of each country’s population against COVID-19 by mid-2022. Meeting that goal will require the vaccination of billions of people across many countries. However, the protection provided by a combination of recovery from previous COVID-19 infection and a single dose of vaccine may offer a way to accelerate achieving that goal and protect populations against the pandemic.
Multiple countries, including France, Germany, Italy, and Switzerland, have required a single vaccine dose following recovery from COVID-19 for an individual to be considered fully vaccinated with a normally two-dose vaccine.
Studies from the United States, the United Kingdom and Israel indicate that for multiple SARS-CoV-2 variants, individuals who have recovered from COVID-19 and received one dose of Pfizer, Moderna, or AstraZeneca COVID-19 vaccine have as much or more immunity to subsequent COVID-19 infection as individuals who have received two doses of those vaccines.
As a result, one dose of vaccine seems to be as good as two for individuals who have had COVID-19. Based on serosurveys – surveys of how many people in different populations have antibodies to the SARS-CoV-2 virus that causes COVID-19 – there are many such people, with at least 700 million estimated to have been infected by the end of 2020 and, unfortunately, many, many more since then.
Multiple countries, including France, Germany, Italy, and Switzerland, have required a single vaccine dose following recovery from COVID-19 for an individual to be considered fully vaccinated with a normally two-dose vaccine. While medical records of past COVID-19 testing results can help, many individuals are not tested for COVID-19 at the time of infection, so tests for signs of past infections are needed as well.
Multiple tests have been developed that can be used for assessing whether or not an individual has antibodies to SARS-CoV-2, a marker of previous infection. Such tests include laboratory-based ELISA tests as well as Rapid Diagnostic Tests (RDTs), which are similar to home pregnancy tests. Given their relative simplicity and ease of use, COVID-19 RDTs can potentially be used in a wide range of settings by a wide range of health workers.
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The Foundation for Innovative New Diagnostics (FIND) has evaluated multiple SARS-CoV-2 antibody tests, including many RDTs, several of which performed very well. The availability of accurate RDTs makes it practical for all countries to follow the model established in France, Germany, Italy, Switzerland and other countries of giving people who have recovered from COVID-19 the option of receiving one dose instead of two doses.
Testing individuals for antibodies to SARS-CoV-2 and then giving individuals that test positive a choice of receiving a single dose of COVID-19 vaccine instead of two doses would allow the acceleration of vaccination efforts in several ways. More people could be vaccinated with a given amount of vaccine, stretching the global supply of COVID-19 vaccine further.
Also, changing a two-dose primary series to a one-dose series would eliminate the need for vaccine recipients to make a return visit to a vaccination site for a second dose. In addition to saving vaccine recipients’ time, this simplification of the vaccine schedule would allow vaccination staff to spend less time on sending vaccination reminders, tracking down people who missed their follow-up appointment, etc., and more time on reaching unvaccinated individuals.
Taking into account whether or not someone has recovered from COVID-19 in immunisation efforts may also help to encourage individuals who believe they have had COVID-19 to be vaccinated. The greater the proportion of a population that has recovered from COVID-19, the bigger the impact of these considerations, so such an approach is most relevant in areas where a sizeable proportion of the population has previously been infected with COVID-19.
Although taking recovery from COVID-19 into account can help to accelerate efforts to protect populations against COVID-19, adaptation over time will likely be required in response to new information and changing circumstances. Given the use of an additional ‘booster’ dose after two doses of Pfizer, Moderna, and AstraZeneca vaccines in multiple countries, including Israel, the United Kingdom and the United States, it will be important to assess how recovery from COVID-19 infection affects the protection provided by such additional doses and thus the value of such doses.
Similarly, the effect of recovery from COVID-19 on the protection provided by other COVID-19 vaccines should be assessed. Since screening potential vaccine recipients for evidence of prior infection would be a new approach for many countries, different countries’ experience with implementing it would provide many insights into how best to do so. In light of the very different circumstances facing different countries, adaptation across countries to account for those circumstances would also be necessary.
Nevertheless, the potential benefits from accelerating the protection of populations against COVID-19 through diagnostic testing to identify people who have recovered from it are substantial.