A new analysis of COVID-19 cases, hospitalizations and deaths from the city health department shows strong effectiveness of the vaccines in preventing serious illness and death, even as the highly infectious delta variant has surged over the summer. 

The analysis found that between January and the first week of August, 96.9% of people hospitalized due to COVID-19 were unvaccinated, and just 0.33% of vaccinated New Yorkers have tested positive for COVID-19. 

About 97.3% of all COVID-19 deaths within that timeframe have been among people who are not fully vaccinated, according to the analysis. 

Even in recent weeks, when the delta variant has led to a rash of breakthrough, albeit relatively mild, cases in vaccinated people, unvaccinated people remain three times more likely to get infected and 13 times more likely to be hospitalized, according to city Health Commissioner Dr. Dave Chokshi. 

Chokshi framed the release of the internal analysis as bolstering scientific evidence that the vaccines effectively combat the delta variant. 

“Although you may have heard anecdotes about breakthrough cases, let's keep in mind that the plural of anecdote is not data,” Chokshi said.

The data included in the analysis are in some cases not accessible through the city’s COVID-19 data portal, and end three weeks ago, even though cases continue to rise in the city due to the delta variant and increased community spread.

Though the analysis is heavily weighted toward the months before June, when a smaller proportion of the city was vaccinated and the delta variant was not as prominent as it is now, Mayor Bill de Blasio said that the analysis still showed clear benefits of vaccination. 

“There's a lot of misunderstanding, a lot of misinformation,” he said. “It’s our job to make things clear.”

Just under 69% of city adults are fully vaccinated, according to city data. De Blasio has announced new rules in recent weeks to spur vaccination, requiring proof of vaccination at restaurants and other venues, and mandating that all Department of Education staff receive their first vaccine dose by late September. 

The delta variant has made considerable gains in the city in recent weeks, and has diminished the overall safety of vaccinated people, the city data analysis shows. 

Between January 17 and June 26, the city saw 5,543 COVID-19 cases among vaccinated residents. By August 7, just six weeks later, that cumulative number had jumped to just under 15,000 - nearly a threefold jump. 

During that same time period, the total hospitalizations of vaccinated people increased from 669 to 1,042, and deaths went from 118 to 153 - gains of about 36% and 23%, respectively. 

Yet the impact on people who were not fully vaccinated when they became infected is even starker. Unvaccinated New Yorkers saw 123 COVID-19 deaths in that six-week period - up to 5,601 from 5,478 - even as the number of unvaccinated residents decreased. 

The share of COVID-19 deaths of unvaccinated people also only declined by about half a percentage point, to 97.34%.

Chokshi said that the data, including information about the delta variant, should encourage even vaccinated New Yorkers to mask in public indoor settings to avoid transmission of the virus to unvaccinated people, such as young children.