The Biden administration announced this week that it will purchase an additional 200 million doses of COVID-19 vaccine from Pfizer and Moderna, meaning the United States will have enough doses of the vaccine to immunize 300 million people ( almost all of the country’s 328 million inhabitants) at the end of the summer.
In clinical trials, these vaccines have been shown to be 94-95% effective in preventing symptomatic cases of COVID-19. There is preliminary evidence that vaccines also reduce asymptomatic infections in people exposed to the virus after vaccination, although more research is needed to confirm this. And, as vaccine distribution intensifies in the coming months, there should be another blessing: a sharp drop in the incidence of severe COVID-19.
“What it would mean for our health care system and for our societies to reduce this serious disease would be huge,” said Stacey Schultz-Cherry, infectious disease researcher at St. Jude Children’s Research Hospital in Memphis. “If we could reduce serious illness, we could kind of get closer to normal.”
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A certain proportion of people are still expected to be vulnerable to infection after being vaccinated against a certain disease, including COVID-19. However, research shows that vaccines can limit the degree of illness in those infected. The seasonal flu shot reduces a person’s risk of being admitted to an intensive care unit or of dying and shortens the length of hospital stays. “Even if the flu shot doesn’t exactly match the strain of virus that is circulating, it will prevent you from getting serious illness,” says Schultz-Cherry. “The same goes for measles; the measles vaccine is excellent for preventing infections and reducing serious illness.
COVID-19 vaccines also appear to reduce the likelihood of people becoming seriously ill if infected. In unvaccinated people, the severity of COVID-19 varies widely, from no symptoms, to mild pneumonia, to life-threatening illness. These extreme cases can involve an overactive or dysfunctional response of the body’s immune system.
“The immune response induced by the vaccine allows the body to control the virus before it reaches the pathologic inflammatory response, the severe disease phase,” says Mark J. Mulligan, director of the Langone Vaccine Center at NYU . “You stop it very early, so maybe there is no disease or just very limited multiplication of the virus.
The virus itself can also wreak havoc by invading tissues all over the body. “It’s really the virus that enters [and] causing damage in addition to other damage your body will cause while trying to fight the virus, ”says Schultz-Cherry. “There are so many different things that we are seeing in these severe COVID patients.”
During clinical trials of COVID-19 vaccines that have received emergency clearance, which includes those from Moderna and Pfizer, researchers looked at a number of criteria for severe COVID-19. These indicators included a pounding heart, ventilator, shock, problems with the nervous system and organs, and admission to the ICU.
In Moderna’s clinical trial, all 30 participants who developed severe cases of COVID-19 were given the placebo instead of the candidate vaccine. During the Pfizer and BioNTech vaccine trial, nine people in the placebo group and one in the vaccinated group developed severe COVID-19. The United States Food and Drug Administration wrote that this participant met criteria for severe COVID-19 because his blood oxygen level was just below normal. However, they were not hospitalized and did not seek further medical attention, the agency noted.
“Vaccines are very effective in preventing serious illness, which basically equates to respiratory failure or impending respiratory failure,” says Mulligan. “It was one of the really impressive aspects of the trials.”
During clinical trials, COVID-19 vaccines prevented demographically serious illnesses, such as age, race, and health status. “So far it seems like he’s doing pretty well across the board, at least in those early days, but there’s always variability in people’s response, whether it’s an infection. or a vaccine, ”says Schultz-Cherry. “One thing we will really need to watch out for over time is whether your COVID antibodies are dropping faster if you belong to a certain demographic.”
However, the level of protection offered by the vaccine is encouraging. “Older people usually don’t respond as well to vaccines,” says Mulligan. “It seems to be a little different here; older adults respond very well to these RNA vaccines. This is crucial, he says, because the elderly are at a higher risk of hospitalization and account for about eight in 10 deaths from COVID-19 in the United States.
Researchers only had the opportunity to track the new coronavirus for about a year. They are still working to understand long-term COVID-19, which involves symptoms that persist for weeks or even months after the initial infection. There are also fears that the virus could cause damage in seemingly mild cases that will emerge later. “One of the scary things about this virus is that we really don’t know, if you have a severe or a mild infection, what that means in the long run,” says Schultz-Cherry.
However, she and Mulligan are optimistic that the vaccines will be able to prevent both severe COVID-19 and the potential for lingering complications. “If the vaccine keeps you from getting infected, which means you don’t have any viruses replicating in your airways, then yes, it would absolutely protect you from these complications in the long run,” says Schultz-Cherry. “Even if you still have viruses that are replicating themselves, but they are much weaker or they cannot penetrate deep into your lungs, I would also predict that you would have fewer complications in the long term.”
Early data also indicates that Moderna and Pfizer vaccines will be effective against new variants of the virus, such as the one recently identified in the UK. The vaccines may be a little less potent against another variant of the virus that has emerged in South Africa, but elicit antibody responses that are likely to stay high enough to provide protection. “Even though it’s a little less effective, I think it will still do a good job of preventing and limiting the severity of the disease,” says Schultz-Cherry.
However, it will be important to continue monitoring the new coronavirus even as vaccines become more accessible. As the virus continues to mutate over time, Mulligan says, “We may see some erosion of absolute protection against lab-confirmed COVID or perhaps the ability to prevent serious illness.”
In addition to preventing people who contract COVID-19 from contracting life-threatening diseases, the ability of vaccines to prevent severe cases will be key to stemming the pandemic. “If the severe illness somehow reflects a higher level of the virus, these people may be more contagious,” says Mulligan. “[By] By preventing severe cases, there can be less transmission of the virus and people are more likely to recover than to die.
Currently, severe COVID-19 is putting great strain on health systems across the country. Earlier this month, hospitals in Los Angeles were forced to prepare to ration care as severe cases increased. Many doctors, nurses and other health care workers struggle with burnout. Clinical trials and elective procedures for other conditions have been halted.
“We need to reduce the number of people infected and, more importantly, if someone is to be infected, we need to make sure that we can reduce the severity of the disease,” says Schultz-Cherry. “Because that’s the devastating thing about infection, is that you can get very serious illness, especially in certain high-risk groups.”