ALBANY COUNTY — A study of data from May to November 2021 in New York State and California coronavirus cases found that, by early October, people who had survived an earlier infection had lower case rates than people who were vaccinated only.

In that May to November time period, the data showed, case and hospitalization rates were highest among unvaccinated people without a previous diagnosis. Before Delta became the predominant variant in June, case rates were higher among people who survived a previous infection than people who were vaccinated alone.

The study was published on Wednesday as part of the Center for Disease Control and Prevention’s Morbidity and Mortality Weekly report, which noted, “Data are limited regarding the risks for SARS-CoV-2 infection and hospitalization after COVID-19 vaccination and previous infection.”

One of the study’s authors is New York’s acting health commissioner, Mary T. Bassett, M.D. The study was conducted before the Omicron variant emerged.

“Similar data accounting for booster doses and as new variants, including Omicron, circulate will need to be assessed,” the study says. “The understanding and epidemiology of COVID-19 has shifted substantially over time with the emergence and circulation of new SARS-CoV-2 variants, introduction of vaccines, and changing immunity as a result.”

Two previous United States studies found more protection from vaccination than from previous infection during periods before Delta predominance just as with the early period of the recently-released New York-California study. Also, as in the present study after July, recent international studies have shown increased protection in people with previous infection, with or without vaccination, relative to vaccination alone.

“Across the entire study period,” the recently released study concludes, “persons with vaccine- and infection-derived immunity had much lower rates of hospitalization compared with those in unvaccinated persons.

“These results suggest that vaccination protects against COVID-19 and related hospitalization and that surviving a previous infection protects against a reinfection.

“Importantly, infection-derived protection was greater after the highly transmissible Delta variant became predominant, coinciding with early declining of vaccine-induced immunity in many persons.”

The CDC had this to say about the implications of the report for public-health practice: “Although the epidemiology of COVID-19 might change as new variants emerge, vaccination remains the safest strategy for averting future SARS-CoV-2 infections, hospitalizations, long-term sequelae, and death. Primary vaccination, additional doses, and booster doses are recommended for all eligible persons. Additional future recommendations for vaccine doses might be warranted as the virus and immunity levels change.”

Breakthrough cases

When a fully-vaccinated person contracts COVID-19, it is termed a breakthrough case. The state’s health department has now updated its report on breakthrough cases based on data received through Jan. 17 and found:

— 1,023,704 laboratory-confirmed breakthrough cases of COVID-19 among fully-vaccinated people in New York State, which corresponds to 7.7 percent of the population of fully-vaccinated people 12 years or older; and

— 30,005 hospitalizations with COVID-19 among fully-vaccinated people in New York State, which corresponds to 0.23 percent of the population of fully-vaccinated people 12 years or older.

“These results indicate that laboratory-confirmed SARS-CoV-2 infections and hospitalizations with COVID-19 have been uncommon events among the population of people who are fully-vaccinated,” the report says.

More than a quarter of Albany County residents are not fully vaccinated.

The health-department data also shows vaccine effectiveness declining over time.

For the week of May 3, 2021, the estimated vaccine effectiveness shows fully-vaccinated New Yorkers had a 92.6 percent lower chance of becoming a COVID-19 case, compared to unvaccinated New Yorkers, the health department says.

Although this effectiveness measure declined through mid-July, this decline then plateaued at about 80 percent after the Delta variant became predominant.

Beginning the week of Dec. 13, 2021, after the emergence of the Omicron variant, vaccine effectiveness against cases began to decline again. In the most recent week, vaccine effectiveness was 77.8 percent. This means fully-vaccinated New Yorkers had about a 78 percent lower chance of becoming a COVID-19 case, compared to unvaccinated New Yorkers, the health department says.

However, when it comes to hospitalizations, the vaccine is doing its job. Across the time period of analysis, fully-vaccinated New Yorkers had between a 90.8 percent and 97.5 percent lower chance of being hospitalized with COVID-19, compared to unvaccinated New Yorkers, the health department says.

The department advises: “Because vaccines do not offer 100% protection, additional protective measures, such as mask wearing, and social distancing will provide additional protection.”

Albany County

Two more Albany county residents — a man in his sixties and a woman in her eighties — died of COVID-19 on Wednesday, Albany County Executive Daniel McCoy reported in his daily COVID release on Thursday morning.

This brings Albany County’s death toll from the virus to 495.

“This is now the fifth consecutive day we’ve announced at least one person losing their life to COVID complications, and these latest two bring our total so far for the month of January to 25,” said McCoy in the release. “And while every death is a tragedy, we had reported 57 deaths in the first 20 days of the month last year.

“We are in a much better position this year, and I continue to encourage people to get vaccinated and get the booster, which have helped us get to where we are and provide important protections against the virus.”

 As of Wednesday, 79.9 percent of all Albany County residents have received at least one dose of the vaccine, and 72.4 percent are now fully vaccinated. The first-dose vaccination rate for county residents 18 and older is now at 88.6 percent.

McCoy also announced 608 new cases of COVID-19. The county’s seven-day average of new daily positive cases is now down to 815.5. Albany County’s most recent seven-day average of cases per 100,000 is now down to 176.9 and its average percent positivity rate is at 17.2 percent.

There were 19 new hospitalizations since Wednesday, and there are now 123 county residents hospitalized with the coronavirus — a net increase of two. Twelve of those hospital patients remain in intensive-care units.