Is the US escaping the last wave of COVID-19 infections?

Increased immunity along with gradual changes in people's behavior contributed to the decline of the epidemic in the US. But there is still uncertainty ahead.

Vaccination for people in San Francisco, California. Photo: NYT
Vaccination for people in San Francisco, California. Photo: NYT

The Delta variant caused a serious outbreak in the US in the early summer. But the epidemic is showing signs of remission. The US currently records an average of 90,000 new cases per day, down 40% from the peak in August. The number of hospitalizations and deaths from COVID-19 also decreased accordingly. The American people expected the worst to be behind.

Winter is approaching, but there are reasons to be optimistic. About 70% of adults in the US have had two doses of the vaccine. A vaccination campaign will also be rolled out for children under 12 over the next few weeks. Regulators may also soon authorize the use of the first anti-COVID-19 pill developed by Merck.

However, scientists warn that the pandemic is not over yet. Every day in the US there are still nearly 2,000 deaths from the disease and a new outbreak in the winter is likely. According to experts, there are still many Americans who have not been vaccinated and there are still many points that cannot be clarified. So it is too early to lift basic epidemic prevention measures.

Flatten the curve by changing behavior

When the first wave of COVID-19 hit the US in early 2020, there was no vaccine and no one was immune to the virus. At that time, the only way to flatten the pandemic curve was to change human behavior. That's why the US issued an order to ask people to stay at home, close businesses, make masks mandatory and ban mass gatherings to repel the first wave.

There is still controversy about what is the most effective measure at that time. But many studies show that basically all the measures have worked, keeping people at home and preventing the number of cases from increasing. These policies combined with voluntary social distancing have basically helped prevent and reverse the first wave of the COVID-19 epidemic in the US.

After the number of cases decreases, measures will be lifted and memories of the epidemic will fade, said Jennifer Nuzzo, an epidemiologist at Johns Hopkins University. At some point, when the number of infections increases again, the same anti-epidemic method will be used now. Businesses and local governments will re-impose restrictions.

For example, during the winter wave of 2020, the percentage of people going to bars, restaurants or attending big events has decreased. “The epidemic curve is shaped by public perception. We keep getting dragged into a crisis and then complacent,” said Nuzzo.

Delta variant appeared when the US when most of the people were too tired of the disease and also the time when vaccinated people felt more secure about the disease. Research data shows that the occurrence of the Delta variant produced less behavioral changes in people compared to previous epidemic waves.

Testing for COVID-19 in a mobile vehicle in Manhattan, New York. Photo: NYT
Testing for COVID-19 in a mobile vehicle in Manhattan, New York. Photo: NYT

As of mid-July, only 23% of Americans said they always wear a mask in public, the lowest percentage since March 2020 - according to the results of a survey conducted by the Institute for Health Metrics and Evaluation under the Ministry of Health. done by the University of Washington. By August 31, the peak of the wave due to the Delta variant, that number had increased to 41%, but still much lower than the rate of 77% during the winter wave of 2020.

Increased immunity and forecast for winter 2021

Behavior change is a temporary and short-term measure to reduce the number of cases. Ending the pandemic will require immunity.

Delta variant transmission is a large, widespread outbreak that first emerged after a vaccine was introduced into widespread vaccination in the United States, giving many adults a better layer of protection. The Delta variant is highly transmissible, causing it to spread rapidly in vulnerable communities and thereby confer natural immunity to many unvaccinated Americans.

Immunity – whether through a vaccine or due to a previous illness, cannot create a layer of protection against the virus completely. But it is that immunity that greatly reduces the risk of infection. So in September, the virus has a harder time finding a host to infect. "The Delta variant is running out of people to infect," said Jeffrey Shaman, an infectious disease epidemiologist at Columbia University.

A decrease in the number of cases does not mean that a country has reached the threshold of herd immunity - a goal many scientists currently consider unattainable. However, increased vaccine coverage and continued transmission of infections when combined with behavioral changes will likely help put an end to infection. "It's a combination of immunity, but people still need to be vigilant," said Joshua Salomon, an infectious disease expert at Stanford University (USA).

It is difficult to say for sure what will happen this winter. Many scientists warn that the number of new cases may not continue the downward trend. Britain and Israel, both countries with higher vaccination rates than the US, are still facing disease outbreaks. “This is a wake-up call. Don't think the pandemic is over," said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

Most experts say it will not be too surprising if there is a disease outbreak, an increase in COVID-19 cases in late autumn or winter this year when people spend a lot of time in activities. indoors and travel during the holiday season.

But because vaccines are still highly effective in preventing hospitalizations and deaths, any spike in cases next winter will be less severe than in 2020. “If the outbreak occurs this winter, it will be worse. not as 'deadly' as last winter, except we're unlucky enough to encounter a new variant," said Dr. Salomon.

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