NYS DOH announces new study, new data website on COVID-19 reinfection
ALBANY, N.Y. » The New York State Department of Health recently announced the publication of the largest comparative study of its kind on immunity to COVID-19 from vaccines and from previous infection, continuing its groundbreaking work on vaccine effectiveness.
The study, which also contains new data on reinfections, was conducted in collaboration with researchers from the California Department of Public Health and the Centers for Disease Control and Prevention (CDC), and published in the CDC’s Morbidity and Mortality Weekly Report (MMWR). It found that both vaccination and a prior infection provided protection against future infection and hospitalization.
Researchers found that from May to Nov. 2021, COVID-19 cases and related hospitalization were substantially lower among those who had been vaccinated and/or survived a previous infection, compared to those who were unvaccinated and without a previous infection. The study concluded that although after the Delta variant emerged, new infections and hospitalizations were lowest among people with prior infection, especially those who were also vaccinated.
The results show vaccination remains the safest way to prevent future COVID-19 infections and severe outcomes, including death. Since the beginning of the pandemic, more than 63,500 New Yorkers have died from COVID-19.
“This study conducted by our premier scientists continues to underscore the importance of vaccination as a critical tool in the COVID-19 response,” study co-author and State Health Commissioner Dr. Mary T. Bassett said.
“Although the epidemiology of this virus may continue to change as new variants emerge, vaccination remains the safest way to prevent infection, hospitalization and death. We continue to urge every eligible New Yorker to get vaccinated and boosted, wear a mask and take every step possible to protect yourselves and your loved ones,” Bassett noted.
The study is based on more than 32 million adults who had at least one COVD-19 test, grouped as follows:
• Group 1: Unvaccinated with no previous laboratory-confirmed COVID-19 diagnosis;
• Group 2: Vaccinated (14 days after completion of a primary COVID-19 vaccination series) with no previous COVID-19 diagnosis;
• Group 3: Unvaccinated who survived a previous COVID-19 diagnosis; and
• Group 4: Vaccinated who survived a previous COVID-19 diagnosis.
During the study period of May 30 through Nov. 20, 2021, new COVID-19 cases in both states were highest among unvaccinated people without a previous COVID-19 diagnosis compared with the other three groups. After the Delta variant became prominent in late June and July, case rates were lower among those vaccinated with no previous COVID-19 diagnosis, and lowest among the two groups with a previous COVID-19 diagnosis.
For example, in New York State in the week beginning Oct. 3, unvaccinated people without a previous COVID-19 diagnosis, were 4.5 fold more likely to have a positive COVID-19 test than vaccinated people without a previous COVID-19 diagnosis (Group 1 vs. 2), 14.7-fold more likely than unvaccinated people with a previous diagnosis (Group 1 vs. 3), and 19.8-fold more likely than vaccinated people with a previous COVID-19 diagnosis (Group 1 vs. 4).
During the same period, compared with unvaccinated people without a previous COVID-19 diagnosis, numbers and hospitalization rates in California followed a similar pattern. For example, during Oct. 3—16, hospitalization rates among unvaccinated people without a previous COVID-19 diagnosis were 19.8-fold higher than among vaccinated people without a previous COVID-19 diagnosis (Group 1 vs. 2), 55.3-fold higher than among unvaccinated people with a previous COVID-19 diagnosis (Group 1 vs. 3), and 57.5-fold higher than among vaccinated people with a previous COVID-19 diagnosis (Group 1 vs. 4).
These results, in two large states that comprised onein-six U.S. deaths from COVID-19 through the end of Nov., suggest that vaccination protected against infection and related hospitalization, but also that surviving a previous infection protected against reinfection and hospitalization. These findings apply to the period before the emergence of the Omicron variant and the widespread use of booster doses.
Becoming vaccinated and staying up-to-date with booster doses remains the most effective and only recommended way to gain immunity to COVID-19. Getting infected carries serious risks, including hospitalization and death, and makes it more likely that you will give others COVID-19, including people who are most at risk of hospitalization and death.
“This analysis represents another chapter in our ongoing studies of this virus and the most effective ways to be protected from illness. Our knowledge evolves along with the virus and together with our public health partners, we will continue to study these issues in order
to best inform and protect the public,” Senior study author Dr. Eli Rosenberg of the Department of Health explained.
This work comprises an unprecedented examination of reinfections, which are new infections among those with a previous COVID-19 diagnosis. To provide ongoing information on reinfections to the public, the Department also announced the launch of a new dashboard with data on COVID-19 reinfection in New York State. The Department similarly launched a pioneering dashboard on breakthrough data after the publication of its study on vaccine effectiveness last year.
Data from the new Reinfection Dashboard extend the results from the new study to illustrate that while reinfections have historically been uncommon, the number increased in Dec. 2021 as the Omicron variant emerged in New York State. This information will continue to be important in understanding the extent of infection in New York State during the current wave, complementing the other dashboards available on the Department’s webpage.
Updates to this Reinfection Dashboard will be published weekly.