The steadily increasing number of New Yorkers getting vaccinated against COVID-19 is preventing the state’s coronavirus infection rate from rising significantly, but the continued spread of the virus among unvaccinated people is preventing it from falling, experts say.
"It’s just a matter of time" that the positivity rate falls, said Dr. Bruce Farber, chief of infectious diseases at North Shore University Hospital and Long Island Jewish Medical Center. "Each week that more and more people get vaccinated, that should influence the overall curve."
The state rate of positive coronavirus tests was falling for weeks after reaching a seven-day average of 7.9% on Jan. 4 following weeks of holiday gatherings — but then remained stuck between 3.1% and 3.2% since late February before beginning to slowly climb again on Sunday. It was at 3.26% on Thursday.
The 13% of state residents who are fully vaccinated is keeping the positivity rate from increasing further, and it masks the rising risk for those who are not vaccinated, Farber said.
"There are more contagious variants that are continuing to spread, making those who are unvaccinated at higher risk for infection, in addition to which society is loosening up significantly," he said, referring to Gov. Andrew M. Cuomo’s recent moves to lift restrictions on some types of gatherings and increase maximum capacity at restaurants and events.
Cuomo on Thursday announced that the Mets and Yankees could play home games with up to 20% capacity, with fans needing a negative test result or proof of vaccination.
Fewer cases seen among older adults
Sean Clouston at Stony Brook University monitors new infections in Suffolk County and is seeing a dramatic drop in positive test results for older adults, a reflection, he said, of widespread vaccinations among them.
"There’s been a shift in the age distribution of the cases," said Clouston, an associate professor of public health. "Now our fastest growth is in much younger cases."
Clouston worries that many unvaccinated people are hearing encouraging news about the pandemic and are beginning to "feel safe," and not following precautions like mask wearing and social distancing as much as in the past.
"The problem is we have these variants, and they are growing in the populations that are not yet vaccinated, because that’s who’s available to them in essence," he said. "That’s a lot more younger people, people who are not acting careful and still lack a vaccine."
With a growing number of more vulnerable people being vaccinated, hospitalization and death rates should eventually drop, Clouston said. The younger people now disproportionately contracting the virus are less likely to get sick enough from COVID-19 to be hospitalized, he said.
Dr. Alan Bulbin, director of infectious diseases at St. Francis Hospital & Heart Center in Flower Hill, is concerned that spring break travel and socialization could push up infection numbers. But, he said, as the weather turns warmer, more interactions will be outdoors, where the risk of virus transmission is lower, and "the numbers will reflect that, just like last summer."
The positivity rate was at 1% or below for most of last summer, daily COVID-19 deaths were typically in the single digits, and hospitalizations statewide fell to 410 on Sept. 10, compared with 4,527 on Thursday.
Data: Vaccines lower transmission risks
Although the vaccines are highly effective in preventing serious COVID-19 illness and death, some vaccinated people contract the virus. But recent data suggests that the vaccines significantly lower the risk of a vaccinated person transmitting it to others.
Pfizer announced March 11 that the vaccine it developed with BioNTech has been 94% effective in Israel — which has the world's highest vaccination rate — against infections without symptoms two weeks after the second vaccine dose is taken.
An Israeli study posted on medRxiv Feb. 8 found that although thousands of people who received the Pfizer-BioNTech vaccine tested positive, the amount of virus they had was on average four times lower for those tested 12 to 28 days after the first dose was given compared with those tested beforehand.
"These reduced viral loads hint to lower infectiousness," researchers wrote in the study, which has not been peer-reviewed.
Scientists believe that someone with lower amounts of virus is less likely to infect others. Other studies and data analysis indicate that other COVID-19 vaccines also can prevent infection and reduce the viral load.
Even so, vaccinated people should still wear masks and practice social distancing, especially around the most vulnerable, Clouston said.
"The danger is that there are some people who are asymptomatic carriers who can spread it, and if they do start passing COVID asymptomatically, it will reach all of the corners of our Island and hit people who are unvaccinated," he said.
As more people get vaccinated, the risk of unvaccinated people contracting the virus will fall, Farber said.
But, he warned, "It depends upon who you’re hanging out with. If you’re going to parties with 25-year-olds, none of whom are vaccinated, then you’ve got to keep that in mind."