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The recent success of some coronavirus vaccines in end-stage clinical trials has brought us to the end of the pandemic, a glimmer of hope in a long year of living with the virus.
Now, the U.S. Food and Drug Administration is preparing to consider emergency use authorization for Pfizer and BioNTech’s COVID-19 vaccine on Dec. 10 and for Modern on Dec. 17. But there are still crucial questions about how these and other vaccines will work. inject yourself into people around the world.
Although vaccinated people, especially those at higher risk for worsening COVID-19 complications, could soon be protected from serious illness and death, it is possible that the shots still do not indicate a return to normal life.
Here you need to know about these first vaccines and what their implementation could mean.
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Q: Can you still get infected and infect others if you get vaccinated?
A: Possibly. None of the vaccines tested so far have been 100 percent effective, so some vaccinated people can still catch the coronavirus.
What’s more, neither Pfizer nor Moderna vaccine trials have tested whether vaccines prevent people from becoming infected with the virus. Those trials, instead, focused on whether people were protected from developing symptoms of the disease. This means that it is unclear whether vaccinated people can still develop asymptomatic infections and therefore can still transmit the virus to other people.
In both trials, some people who received the vaccine became ill with COVID-19, but not as sick as those who received placebo. One vaccine receptor became seriously ill in the Pfizer study compared with nine in the placebo group (SN: 18/11/20). No one who received the Modern vaccine became seriously ill, while 30 people who received the placebo developed serious illnesses (SN: 30/11/20).
In a separate trial, AstraZeneca and Oxford University reported that they found fewer asymptomatic cases among people who had received the vaccine than in a comparison group (SN: 23/11/20). This may suggest some protection against infection and disease. But it remains to be seen how any of these vaccines actually affect transmission.
It is important to remember that COVID-19 cannot be obtained directly from the vaccines being evaluated now as none of them contain the complete virus.
Q: So how useful are these vaccines?
A: These vaccines appear to reduce the likelihood that a person will have symptoms if they are infected, as well as the severity of the disease. This could be a huge help in keeping people out of hospitals, preventing deaths, and perhaps reducing some of the long-term side effects of COVID-19. These include heart and lung problems that some people develop after an attack of the disease.
It is true that an ideal vaccine would reduce the risk of transmission. But not everyone does. Influenza vaccines, for example, may not protect against all infections, especially when those vaccines do not match perfectly with the virus strains that circulate each year. At other times, the shots decrease the chances of infection, but do not completely eliminate it because influenza viruses mutate rapidly and can slip through immune defenses erected even by well-combined vaccines. But even imperfect vaccines can make flu illnesses less severe.
Q: Will people still need to wear a mask and social distance after getting vaccinated?
A: Yes. It takes several weeks to build vaccine-induced antibodies and other immune defenses, and both Pfizer and Moderna vaccines require a booster dose between 21 and 28 days after the first dose. Therefore, the full protection that vaccines offer would take at least a month to develop.
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And since vaccines don’t work perfectly and it’s not yet known if they prevent infection, it’s possible that a vaccinated person can get the virus and be able to pass it on to other people.
While vaccines can help control the pandemic, "people need to understand that this is not a magic wand," Peggy Hamburg, a former FDA commissioner, said Dec. 3 during a news conference hosted by SciLine, a service independent and free for journalists based at the American Association for the Advancement of Science. "It doesn't mean we can suddenly give up all the other activities that were so important to reducing infection rates."
In other words, people will still have to wear masks, walk away socially, wash their hands, and avoid large gatherings, especially indoors. Also, it will take time to vaccinate everyone. Until that happens and until it is clear how well vaccines prevent transmission, further safety measures will still be needed, Hamburg stressed.
Q: Are these vaccines safe?
A: So far, they seem safe. Most vaccine side effects occur in the first few weeks or months after the vaccine, which is why the FDA has required companies to have two months of safety data before applying for emergency use authorization.
Data collected in clinical trials indicate that vaccine side effects include fever, headache, arm pain, redness at the injection site, and a feeling of being deteriorated. These side effects are common in vaccines approved for other diseases.
“Those are things we expected and we were very reassured that we didn’t see cases of things we wouldn’t expect,” said C. Buddy Creech, director of the Vanderbilt University Vaccine Research Program in Nashville. Creech, who participates in Phase III clinical trials testing the safety and efficacy of the Modern vaccine, as well as Johnson & Johnson, spoke Dec. 3 during a press conference sponsored by the Infectious Diseases Society of America.
Even after the vaccines are released to the public, government regulators, healthcare organizations and manufacturers will continue to collect safety data.
Q: When can groups such as children or pregnant women be vaccinated?
A: Neither vaccine has been tested yet in children under 12 or in pregnant women, so both groups are likely to be near the back of the vaccination line.
Kathleen Neuzil, of the University of Maryland School in particular, women of childbearing age make up a large proportion of health workers and front-line workers, "so we don't really have a vaccine for everyone until we have a vaccine for pregnant women." of Medicine in Baltimore during the Society of Infectious Diseases press conference on December 3rd.
Researchers have been waiting to obtain data from animal studies on how vaccines can affect reproduction and development before testing in pregnant people. Some companies are already nearing the end of these studies and may begin testing vaccines on pregnant women soon, said Neuzil, who is director of the Center for Vaccine Development and Global Health at the medical school.
For the children, most researchers waited to find out the effectiveness of the vaccines. Now that at least the first vaccines report high efficacy in preventing symptoms, the benefit of vaccinating probably outweighs the risks, making companies more comfortable testing in children.
Pfizer has tested its vaccine in teens 12 years of age and older, and Moderna plans to do so soon. This is typical of the vaccine testing process, which begins with healthy adults and works even in teens and then in younger children, William Moss of the Johns Hopkins Bloomberg School of Public Health in Baltimore said Dec. 3.
Moss, who is executive director of the International Vaccine Access Center in Johns Hopkins, said he hopes that by the fall school year in 2021 there will be a vaccine for children 12 and older. By then, “I think we have a good chance of having a vaccine for younger children as well,” he says.
Q: Can these vaccines help us achieve herd immunity?
A: Scientists are still figuring out how many people must have immunity to the virus to starve from susceptible host outbreaks and end the pandemic. Most estimates fall between 60 and 80 percent of the population, although the number of people who will need to be vaccinated to get to this point is still unclear and depends on the effectiveness of the vaccine.
If vaccines were to be as effective as possible in disease prevention and transmission, it would be sufficient to vaccinate with enough people to accurately reach the herd’s immunity threshold. But less effective vaccines require more people to be vaccinated, to take into account possible gaps in immunity.
In general, some vaccines are more effective in reducing the severity of the disease than reducing transmission. And as we noted earlier, it’s still unclear how vaccines like those from Pfizer and Moderna affect transmission. If these vaccines do not prevent transmission at all, achieving herd immunity through vaccination becomes impossible. But this scenario is highly unlikely: by reducing the severity of the disease, vaccines are likely to decrease transmission by reducing the number of days a person launches an infectious virus, for example. For now, scientists are waiting for more data.
Although vaccines end up reducing transmission effectively, achieving herd immunity worldwide will require an equitable distribution of vaccines, which will be a challenge given the logistical requirements of the current list of vaccines (SN: 12/3 / 20). If people living in poorer, more rural areas are unable to access vaccines, outbreaks can persist in these regions and prevent a definitive end to the pandemic if the problem becomes widespread.
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