Last week, President Joe Biden said his government’s goal was to “get the country closer to normal” by the fourth of July.
Although the US appears to be moving in the right direction – for example, a majority of people over the age of 65 have received at least one dose of vaccine – scientists following the pandemic say it is critical to look separately. at every state, even every city.
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“If you consider it a monolithic event, you will miss a lot of details,” said Dr. Thomas Giordano, head of infectious diseases at Baylor College of Medicine in Houston, said.
Giordano views the Covid-19 outbreak in the US as a “series of micro-pandemics.”
“What happened in Houston was not the same as what happened in New York or in Phoenix or LA,” he said. “They had different curves, and different mortality rates.”
A variety of statistics could indicate that the country is getting the pandemic under control, including the number of new daily cases and the number of deaths. But epidemiologists say that three specific measures are needed to gain a clear understanding of the country’s general response: the number of hospitalizations associated with Covid-19, the so-called reproduction number of the virus and the number of vaccinations administered.
Hospitalizations
Scientists have been relying for months on the number of positive Covid-19 tests taken in a particular community – known as ‘percent positivity’ – as an indication of the severity of the outbreak.
But over time, the criterion may lose importance. The percentage of positivity will change based on how many people are tested, Giordano said. The number of tests “will decrease as we vaccinate more people,” he said, “and people will be less likely to be tested.”
One way to circumvent the problem is to focus instead on Covid-19-related hospitalizations.
“The hospitalization rate is, in my opinion, the most difficult and fastest number,” said Cameron Wolfe, an associate professor of medicine at Duke University School of Medicine.
No matter what we have done over the past year, we have not raised the chance that someone who gets Covid will need hospital support.
“No matter what we have done over the past year, we have not raised the chance that anyone receiving Covid will need hospital support,” Wolfe said. This means that hospitalizations are still a good representation of common cases in any community.
Hospitals are also continuing to test Covid-19, which gives another snapshot of the spread of the community.
“Every hospital in the country examines every patient who comes in for Covid-19,” no matter what problem the patient brought to the hospital, such as a heart attack, Dr. Timothy Brewer, an infectious disease expert and professor of epidemiology at the UCLA Fielding School of Public Health.
“People who are sick enough to go to the hospital go, whether they are worried about Covid or not,” Brewer said.
Reproduction number
The reproduction number of a virus indicates how many people a single sick person is likely to infect.
Scientists usually calculate the number based on several factors: how many people are still susceptible to a disease, how many people are currently infected and how many people have some degree of immunity through infection or immunization.
The reproduction number can be calculated in different populations, for example at state or city levels, and it can vary over time.
The lower the number, the better – and less than 1 is best.
A reproduction number above 1 means that one sick person is likely to transmit the virus to at least one other person, said dr. Richard Medford, co-principal medical information officer at UT Southwestern Medical Center in Dallas, said. (For example, a reproduction number of 2 means that one infected person will transmit the virus to two other people.)
This is a problem because it indicates that the outbreak will continue to worsen. “When we see the reproduction rate increase, we’m worried,” Medford said.
Conversely, if the number is less than 1, it is an indication that the community is in a better state. This would mean that a single person would probably not transmit the virus to one or more people.
Vaccines
In the long run, the number of vaccinations administered is the measure that will be the most progress in the country.
“How many vaccines can we get in our arms? That’s really how I can determine how well we’re doing,” Medford said.
The Centers for Disease Control and Prevention reported Wednesday that 111 million shots had been fired nationwide. But scientists say it is important to go past the raw number to find out who is really rolling up their sleeves.
“You can not really look at the total vaccination rates without making sure that all populations have the same level of vaccination. Otherwise you may have small outbreaks,” said Dr. Peter Chin-Hong, a specialist in infectious diseases at the University of Pretoria, said. California, San Francisco.
There can be significant variations in the distribution of vaccines in different parts of the country, as well as in color communities. These details will be critical for epidemiologists to interpret the vaccination numbers in the coming months.
Medford said he would also like to analyze vaccinations according to age. “If you look at seriousness in terms of how many people were hospitalized or how many people died from this disease, it is most important to vaccinate our elderly,” he said.
And the faster vaccinations start, the greater the chance that the country will be able to anticipate emerging variants, especially the B.1.1.7 variant, which was discovered in the United Kingdom.
“This new variant, which is taking over in the United States, is more transferable,” Murphy said. “It’s part of the number of people who need to be immune.”
What about herd immunity?
The more people are vaccinated, the closer the US gets to herd immunity – the point at which enough people are immune to the virus that can no longer spread it. Immunity can come from both vaccinations and past infections.
But the true number of infections in the US can be difficult to determine because many people who have been sick have never been tested. As a result, the epidemiologists with whom NBC News spoke predominantly preferred to focus on vaccination numbers.
“It’s an absolute number,” Medford said. “I can tell without a doubt how many people have been vaccinated, and I know how effective the vaccines are.”
The jury is still looking for the so-called critical vaccination threshold – the percentage of the population that needs to be vaccinated to protect everyone – and that could be a gripping target.
Last year, for example, experts estimated that the US should vaccinate 60 percent of the population. But as the virus spreads more easily, the percentage should rise.
Now it’s closer to 80 percent, just because the B.1.1.7 variant is more transmissible, ‘said Bill Hanage, associate professor of epidemiology at the Harvard TH Chan School of Public Health. “You need to make more people immune to stop the spread.”
Evidence has shown that the current vaccines are effective against the B.1.1.7 variant – even if the shots are not perfect.
“We do not need 100 percent success. We need a solid success of 50 to 90 percent,” Giordano said, referring to the effectiveness of the vaccines. “If enough people achieve 50 percent success, the chances of one person getting really sick from Covid drop.”
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Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, commented during a congressional hearing Wednesday on the use of the term “herd immunity.”
“We have to be really careful with this evasive terminology,” Fauci said. “We need to focus on vaccinating as many people as possible,” he said, rather than concentrating on an ‘arbitrary percentage’.
Ultimately, no single measure will determine when life can become ‘normal’ again.
“I do not think there is a standard that would say, ‘Oh, it’s over,'” Justin Lessler, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health, said of the pandemic.
SARS-CoV-2, the virus that causes Covid-19, is likely to stay here, but it is expected to slowly become more like the flu, which needs annual boosters.
That is, instead of an on / off switch, the end of the Covid-19 emergency in the US will be more or less dimmed.
“It’s going to be an old enemy rather than the plague it is today,” Lessler said.
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