Nearly 100 million Americans are fully vaccinated and new coronavirus cases are at their lowest level since last October. Could the vaccination campaign finally be winning the race against the coronavirus in the United States?
That's the big question the nation has been waiting to answer. While some researchers says it's still too soon to know for sure, a growing number of epidemiologists, infectious disease researchers and public health experts think the country might have reached — or be about to reach — that crucial inflection point.
"I think we've hit a tipping point," says Dr. Ashish Jha, the dean of the Brown University School of Public Health. "We've really turned a corner on this latest wave. And I think that the worst days of the pandemic really are now behind us."
Jha and others base that conclusion on several factors. First of all, a significant proportion of the U.S. population — an estimated 34% — already has some immunity to the virus from having been exposed to the virus.
Secondly — and most importantly — the vaccination campaign has now inoculated a significant number of people. More than 43% of the population has now gotten at least one shot, and a third are fully vaccinated. That's getting very close to where other countries, such as Israel, started to turn the corner and experience a precipitous drop in infections.
The combination of natural immunity from people who were exposed and vaccination "means we may be closer to 60% population immunity already," Jha says. "That's why I'm pretty confident we have turned the corner."
And, in fact, the number of people getting infected every day in the U.S. has finally begun to fall again, after months of rising slowly. Over the past two weeks, the average number of new daily infections has dropped 27%.
"I do think we've hit a turning point," says Dr. David Rubin, director of the PolicyLab at Children's Hospital of Philadelphia. "We're seeing a significant, substantial decline now. And we hope it just deepens over the next few weeks."
Now, not everyone is so optimistic. Infections are finally falling in Michigan. But the virus is still spreading fast there and in other places, such as Oregon, Washington state, and parts of Colorado and Arizona. And many experts worry people are letting down their guard too soon.
"Time will tell," Dr. Thomas Frieden, a former director of the Centers for Disease Control and Prevention, wrote in an email to NPR. "Michigan-like outbreaks remain quite possible until we have more immunity."
"There was a fourth surge, whether it's already receding isn't yet knowable," he adds. "It didn't feel so bad because it was so much smaller than the third. It has been a bit larger than the second, and may not be over yet."
Jennifer Nuzzo, a senior scholar at the Johns Hopkins Center for Health Security, is also cautious. "I think we're getting close to the tipping point, but I want to see a few more weeks of declining cases before I can say that we're there," she says.
But others are more confident the country has reached a long-awaited threshold thanks to vaccination.
"The results of vaccination have been truly astonishing in terms of its value of getting us back to normal and liberating us from this pandemic," Rubin says.
The vaccines look like they've even been able to stave off the threat posed by the variants, including the B.1.1.7 variant, which is the highly contagious strain first spotted in Britain that is now the dominant in the U.S.
"We have created a wall which is preventing the variant, particularly the UK one from the UK and others, from spreading and surging," says Dr. Eric Topol, a professor of molecular medicine at Scripps Research.
The optimism also comes from several mathematical models of the pandemic that try to factor in, among other things, the spread of the variants, the level of vaccination and how much people are following public health guidance such as wearing masks and social distancing.
"The models for every state shows that if the state isn't already in decline, they should start to see a decline in a few weeks," says Dean Karlen of the University of Victoria in Canada, who has been modeling the effect of the variants on individual U.S. states. "And hopefully, we'll start seeing the decline go faster and faster, assuming the vaccination rate continues."
All that said, the country isn't completely out of danger. The number of people getting infected every day remains high. And there are some worrying trends, mostly notably a recent sharp drop-off in vaccinations.
"We're starting to try to vaccinate those who have been a little more hesitant or harder to reach or have been having trouble accessing vaccines," says William Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health. "It is really, really important that we do reach those people."
In addition, vaccination rates vary a lot across the country. A big worry are places where not enough people are rolling up their sleeves, such as some Southern states like Alabama, Georgia and Mississippi.
"If you remember back to last spring, many of the states across the South thought that they had escaped COVID-19. Then it started to get hot. People went indoors into the air conditioning. That was a perfect storm for spread of COVID across our Southern states last summer," says Dr. Megan Ranney, an assistant dean at Brown University.
"I worry because those are the same states where our vaccine numbers are not great. And so it sets them up potentially for a rise in COVID-19 cases again," Ranney says.
So even those who are convinced that the nation as a whole has hit a tipping point acknowledge that individual metropolitan areas, states or regions with low levels of vaccination could experience outbreaks throughout the spring and summer.
And many are predicting another surge could occur in the fall if too few people have gotten vaccinated by then, and people retreat back indoors because of the colder weather.