Study tracks virus’ spread

Unvaccinated individuals who hadn’t had COVID hit hardest, data shows

A study released Wednesday by state and federal health officials found that vaccination and prior infection with coronavirus substantially reduced a person’s chances of reinfection and hospitalization during the six-month period ending Nov. 30.

The period examined by the study is important, as boosters and the extremely contagious omicron variant had yet to circulate widely in the U.S. The study, which includes analyses by state Department of Health scientists, also suggests that prior infection may have played a bigger role than vaccination status alone in preventing infection and hospitalization during the delta wave, which began around late June, than it did during the alpha wave, which occurred the prior winter.

Across the entire study period, however, unvaccinated individuals remained far more likely to get sick and require hospital care than their vaccinated counterparts, the data shows.

“This study conducted by our premier scientists continues to underscore the importance of vaccination as a critical tool in the COVID-19 response,” said acting state Health Commissioner and study co-author Dr. Mary T. Bassett. “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.”

The study, which contains new data on reinfections, was conducted by New York scientists with help from the California Department of Public Health and the Centers for Disease Control and Prevention. It was published Wednesday in the CDC’S weekly morbidity

and mortality report.

Chances of infection high for unvaccinated

The analysis looked at infections and hospitalizations across four groups of people: vaccinated adults with no history of COVID-19; vaccinated adults with a prior COVID-19 diagnosis; unvaccinated residents with no history of the disease; and unvaccinated residents with a prior diagnosis of the disease.

Unvaccinated individuals who had not previously been diagnosed with COVID-19 had the highest infection rates across the entire study period.

Compared to this group, in New York infections were:

▪ 18.4 times lower among vaccinated residents who never had COVID-19

▪ 8.5 times lower among vaccinated residents who previously had COVID-19 A 9.9 times lower among unvaccinated residents who previously had COVID -19

These relationships changed after the arrival of the more severe delta variant last summer, with prior infection appearing to play a larger role than vaccination alone when it came to protecting against infection and hospitalization.

The study notes, however, that those who were unvaccinated and had no history of COVID-19 continued to be the hardest hit.

Compared to this group, and starting the week of Oct. 3 (when delta was in wide circulation), infection rates in New York were:

▪ 19.8 times lower among vaccinated residents with a prior infection

▪ 14.7 times lower among unvaccinated residents with a prior infection

▪ 4.5 times lower among vaccinated residents without a prior infection

“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 study states.

Federal health agencies recommended booster shots of the coronavirus vaccine in September for certain groups, citing the concern of declining immunity. It wasn’t until later in the year, however, that boosters became widely available to large swaths of the population.

Getting vaccinated and staying current on boosters remains the most effective way to gain immunity to COVID-19, the Department of Health said Wednesday. Getting infected carries serious risks, including hospitalization and death, and makes it more likely a person will spread the disease to others, it said.

“This analysis represents another chapter in our ongoing studies of this virus and the most effective ways to be protected from illness,” said Dr. Eli Rosenberg, of the state Department of Health. “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.”

The study was based on more than 32 million adults living in New York and California. Since the beginning of the pandemic, more than 63,500 New Yorkers have died from COVID -19.

New York launched a new dashboard Wednesday featuring its reinfection data, which show the number of reinfections increasing in December as omicron became the predominant variant.