[ad_1]
Vaccine distribution is increasing in many countries, but with a further rise in Covid-19 cases and the prospect of a new wave of infections on the horizon, the world is in a race against time.
The key to winning the race, experts say, is not only whether vaccines will play an important role in preventing serious illnesses caused by Covid-19, but also whether they can stop people from spreading the virus. virus.
“The ideal vaccine would have two performance characteristics: one prevents you from going to the hospital, going to the intensive care unit and losing your life,” said Dr Peter Hotez, co-director of the Center. for Vaccine Development at Texas Children’s Hospital and Dean. from the National School of Tropical Medicine at Baylor College of Medicine. “But if the vaccine also stops the asymptomatic spread, then you could potentially vaccinate to get out of the epidemic.”
Comprehensive coverage of the coronavirus outbreak
So far, the first indications are promising. The effect of vaccines on asymptomatic infection was a big unknown, but scientists say it will be crucial in ending the pandemic.
Asymptomatic cases, which involve people infected with Covid-19 but have no symptoms, are estimated to account for more than half of all transmissions of the virus, according to a recent study published in the journal JAMA Network Open by researchers from the United States. Centers for Disease Control and Prevention. While vaccines can block asymptomatic infections, they could also drastically reduce overall transmission, giving hope that the virus will be contained soon.
Vaccines can protect against transmission by reducing a person’s viral load or the amount of virus in the body, said Dr. Becky Smith, associate professor of medicine at Duke University.
“Theoretically, by lowering your viral load, it should prevent your ability to transmit to others,” she says. “And while that doesn’t completely prevent transmission, it should reduce it considerably.”
The focus on vaccines and transmission comes at an important time in the pandemic. Although cases around the world have been dropping for several weeks, some European countries are now experiencing rebounds. Parts of the United States are also reporting increases, a worrying development given that many states have recently eased public health restrictions.
Concerns about variants of the coronavirus, including strains that may be more contagious, also persist. Senior government infectious disease specialist Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told NBC News’ Richard Engel on Thursday that the United States needs to vaccinate as many people as possible to avoid new epidemics.
Part of this strategy depends on the effect the vaccine might have on reducing transmission.
Last week, new data from Israel, where nearly 60% of the country’s 9 million people have received at least one dose of a vaccine, suggests that the Pfizer-BioNTech vaccine is 94% effective in prevent asymptomatic infections.
A separate study by researchers at the University of Cambridge, UK, found that a single dose of Pfizer vaccine can reduce asymptomatic infections by 75%. The results, which have yet to be peer reviewed, come from an analysis of around 4,400 tests performed on healthcare workers vaccinated in Cambridge over a two-week period in January.
In the Johnson & Johnson trials, the company’s vaccine was shown to be 74% effective against asymptomatic infections. And according to a report released in December by the Food and Drug Administration, early data suggests Moderna’s vaccine may also protect against asymptomatic infections, but the company said more research is needed.
Angela Rasmussen, a virologist at the Georgetown University Center for Global Health Science and Security, said the early findings were “very promising.” But she added that there were still big unanswered questions.
“From the actual data we have so far, it appears that vaccines have an impact on asymptomatic infection,” she said. “The real question, however, is how wide will it be?”
And since vaccines are not 100% effective, it is possible that a small number of people vaccinated will be infected with the virus. If this happens and a vaccinated person is asymptomatic, it is not yet clear whether the person could transmit Covid-19 to others, Rasmussen said.
In a new commentary published Thursday in the journal Science, Rasmussen and Saskia Popescu, infectious disease epidemiologist at George Mason University in Virginia, explain in detail why controlling “asymptomatic transmission” is essential to ending the pandemic. Symptomless transmission includes both people who have no symptoms and those who are pre-symptomatic but later develop symptoms.
“As more and more people get vaccinated, it will have a population-wide effect on transmission, but while the majority of people are not currently vaccinated, we need to be aware of the problem of asymptomatic and pre-symptomatic transmission, “said Rasmussen.
Most scientists agree that there are two main routes out of the pandemic. One is to reach a threshold known as herd immunity – when enough people have developed antibodies from a natural infection or from vaccines, future outbreaks are unlikely. The other is so necessary to curb the spread of the virus that even unvaccinated parts of the population are at little risk of infection.
While vaccines can protect against asymptomatic infection, they could help with the latter, but the two strategies should not be mutually exclusive, Rasmussen said.
Download the NBC News app for comprehensive coverage of the coronavirus epidemic
“It’s really a series of interventions,” she said. “We need to think about ways to reduce overall transmission, and we should not rely exclusively on vaccines.”
One way to reduce overall transmission is to consider public health measures that have been in place throughout the pandemic, such as practicing social distancing, wearing masks and avoiding gatherings with unvaccinated people. If the virus can be adequately contained, some aspects of life could return more to normal even if parts of a population still go unvaccinated, Rasmussen said.
“We don’t need to be on the threshold of herd immunity to relax the restrictions,” she said. “If we can make the virus so rare in the population, there will be no risk of people being exposed to it, whether or not they are vaccinated.”
Source link
