A second coronavirus vaccine has now joined the fight against COVID-19 in the United States.
On December 18, the U.S. Food and Drug Administration authorized the Moderna vaccine for emergency use in people 18 years of age or older. The decision follows a detailed vote by a panel of experts that met Dec. 17 to discuss vaccine data the biotech company had collected from its ongoing clinical trial.
The vaccine joins a similar one from the pharmaceutical company Pfizer and its German partner BioNTech, which was licensed on December 11 and began being administered to people from high-risk groups in the United States, including health care workers and people living in nursing homes. majors (SN: 12/11/20; 01/12/20).
Here’s a look at how the two vaccines stack up with each other.
Both clearly protect people between the ages of 18 and over 65 from developing COVID-19 symptoms.
Both the Moderna vaccine – developed in collaboration with the U.S. National Institutes of Health – and the Pfizer vaccine exceeded expectations in clinical trials.
In documents submitted to the FDA for review, Moderna reported that its Phase III clinical trial, which includes more than 30,000 people, showed that the vaccine was 94.1 percent effective in preventing those who received it from developing symptoms. COVID-19. The biotechnology company has already published the finding, determined two weeks after participants received a second dose of the vaccine, in a press release on November 30 (SN: 16/11/20). The Pfizer vaccine is equally effective in preventing symptoms, with a 95 percent effectiveness.
Comparable results are likely because the pair of COVID-19 vaccines are “much more the same than different,” says Susanna Naggie, a doctor in infectious diseases at Duke University. "I think that's why we're seeing a very similar profile in terms of the first efficacy data."
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For Pfizer, that effectiveness was comparable among the 16- to 89-year-old age groups. Among participants in the Modern Clinical Trial between the ages of 18 and 64, the vaccine was 95.6 percent effective. But in people over 65 it had a lower efficacy of 86.4 percent.
This difference, however, is based on a small number of cases in that older age group (four in the vaccine group and 29 in the placebo group) and is not statistically significant, said Jacqueline Miller, head of Modern infectious disease development. the December 17 FDA advisory hearing. The “effectiveness of the vaccine in the elderly is consistent with its effectiveness in the general population,” he said.
The Moderna vaccine may provide better protection after the first dose.
Although both vaccines require two doses to provide people with the best protection, early evidence indicates that Moderna can do a better job defending symptoms as early as two weeks after the first dose.
Pfizer’s vaccine regimen includes two shots spaced 21 days apart; The two doses of Moderna are separated by 28 days. After people in the Pfizer trial received their first dose, there were 39 cases of COVID-19 in the vaccine group and 82 in the placebo, giving the vaccine an efficacy of 52.4 percent. Moderna, on the other hand, had an efficacy of 80.2 percent after the first dose.
In the Moderna trial, however, that efficacy is based on a relatively low number of cases – 39 in the placebo arm versus seven in the vaccine arm – only in a subset of trial participants. And almost all participants received the second dose of Moderna, which makes it difficult to know for sure how well people are protected from a single injection.
The Moderna vaccine may be best for preventing severe symptoms, but it’s too early to tell.
The Moderna vaccine initially showed an impressive 100 percent effectiveness in preventing severe symptoms in people who received it. While 30 people in the placebo group of the clinical trial developed serious illness, no vaccinated person did. However, since that analysis took place, one person in the vaccine group has been able to develop a serious case, but that is not yet validated, FDA doctor Rachel Zhang said at the Dec. 17 hearing.
Pfizer announced in a Nov. 18 press release that its vaccine appeared to prevent people from becoming seriously ill as well. But there were few cases in that trial to know for sure, experts say (SN: 11/18/20; 10/10/20). Four participants in the Pfizer trial developed severe COVID-19, three of whom received placebo.
Still, “it is very clear for Modern and Pfizer vaccines that symptomatic coronavirus (cases) and coronavirus infections that require hospitalization are drastically reduced,” says Andrea Cox, a viral immunologist at Johns Hopkins University.
Unlike Pfizer, Moderna has preliminary data suggesting that its vaccine stops the infection, not just the symptoms.
Some early data suggest that the Modern vaccine could protect vaccinated people from asymptomatic infections and symptomatic diseases. While it is clear that the vaccine, along with the Pfizer vaccine, prevents people from developing symptoms of COVID-19, completely stopping infections is crucial to curbing the spread of coronavirus and building immunity in communities.
Of the more than 14,000 people who received a placebo, 38 tested positive for coronavirus – asymptomatic – after their first injection but before the second. However, only 14 who received the Modern vaccine were asymptomatic carriers of the virus when those people were tested before their second dose, the company reported. That two-third reduction in asymptomatic COVID-19 cases in the vaccine arm of the trial compared to the placebo group suggests that some infections could be prevented, even after a single dose of vaccine.
Pfizer has not yet released any data to show whether its vaccine prevents asymptomatic cases of COVID-19. But because it works like Moderna’s, “I don’t think there’s any reason to believe there’s a difference between the two,” Naggie says.
Both vaccines use a genetic molecule called mRNA that is enclosed in a nanoparticle to deliver instructions to cells to make the coronavirus ear protein, which the virus uses to break into cells. The immune system learns to recognize and defend itself against the beak when it is in an infection.
Both vaccines cause similar side effects, although doubts about severe allergic reactions remain.
Each vaccine can induce similar side effects after being injected into the body. “It causes arm pain quite universally,” Cox says. Such “systemic” symptoms as fatigue, chills, body aches, or headache were also common among participants in both trials, especially after the second dose.
But “the tenderness, swelling, and (rates of) some systematic symptoms are a little higher” with Moderna’s vaccine than Pfizer’s, Cox says. This could be because Moderna included more mRNA in each dose, causing rapid, strong symptoms as the immune response reacted to foreign material, Cox says.
Such side effects are not uncommon with vaccines. “In fact, it shows that your body is developing a robust immune response, which is exactly what you want,” says Naggie.
There have also been some isolated cases of Bell’s palsy, a temporary weakness or paralysis of the facial muscles, in participants in the trials of both vaccines. More of these cases occurred in the vaccine arms in both the Moderna and Pfizer trials than in the placebo groups, raising concerns that they may occur in response to COVID-19 vaccines.
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But these cases are still rare in general in both arms of the trials, Cox says. And “it’s important to remember that viruses also cause Bell’s palsy,” he says. So it is possible that, although vaccines cause some cases, Bell’s palsy rates may ultimately be lower in vaccinated people than what could happen after a coronavirus infection. At the Dec. 17 hearing, FDA officials recommended to experts that they continue to monitor Bell's palsy for vaccinated people, but they have not yet been able to pinpoint whether the vaccines are behind the cases.
Since the Pfizer vaccine was spread in the United Kingdom and the United States, some health care workers have experienced more severe reactions that did not occur in clinical trials. Two people in the UK had allergic reactions to the vaccine, as did three people in Alaska. The U.S. Centers for Disease Control and Prevention recommends that clinics control people’s allergy symptoms after vaccination and have treatments like adrenaline on hand.
It is unclear whether similar allergic reactions will occur in people receiving the Moderna vaccine. One consideration is that the nanoparticles used in both vaccines are different, Tal Zaks, Medical Director of Moderna, said at the Dec. 17 FDA hearing. That difference could mean that the nanoparticle in Moderna’s vaccine does not have the same potential as Pfizer’s to cause allergic reactions. But some experts suspect that allergic reactions may be due to a component of the nanoparticle called polyethylene glycol, which is found in both vaccines.
More doses of Moderna vaccine will initially be available in the United States.
In July, Pfizer agreed to supply 100 million doses of COVID-19 vaccine to the United States by the end of March 2021, enough to vaccinate 50 million people, as each vaccination requires two shots. But officials refused to buy more of that vaccine when given the option, limiting the number of initial doses available. Some bottles of Pfizer, which are usually filled with five doses of the vaccine, contain more than the allotted amount, the FDA said via Twitter on Dec. 16. Officials advise using all full doses of each vial, allowing health workers to vaccinate more people.
Modern, on the other hand, plans to deliver 200 million doses in the United States, enough to vaccinate 100 million people by the end of March. Of these, the company plans to ship about 20 million doses by the end of 2020. Another 80 million will be delivered in the first quarter of 2021.
The Moderna vaccine doesn’t have to stay that cold, so it should be easier to distribute.
A big distinction is how vaccines should be stored. The Pfizer vaccine should be kept in special freezers at ultra-cold –70 ° C, while the Moderna vaccine is fine at a standard freezer temperature of –20 ° C (SN: 20/11/20). The Moderna vaccine can also survive up to a month in a refrigerator. Because Modern vaccine doses can be stored at higher temperatures, their distribution should be easier to control than that of Pfizer.
“I think it’s good that we have some flexibility here,” Naggie says.
Some hospitals are able to keep the Pfizer vaccine in ultra-cold storage for long periods of time until those doses are thawed for use. Clinics that do not have ultra-cold freezers can resort to shooting from Moderna. And in the future, there will also be vaccines from other companies – like AstraZeneca or Johnson & Johnson – that can be kept in the fridge even longer.
For now, it’s exciting to have two vaccines available, says Naggie, who received his first dose of Pfizer’s COVID-19 vaccine on Dec. 16. "Being in line to get my vaccine … there's a sense of hope and I think it's amazing."
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