NEW YORK: US regulators authorized Moderna Inc’s Covid-19 vaccine for emergency use on Friday, a week after granting the first US authorization for Pfizer Inc and the BioNTech SE coronavirus vaccine.
The following is a comparison of the two vaccinations and what to expect when both are available:
How are vaccines alike?
Both vaccines use messenger RNA (mRNA) technology, which contains instructions for human cells to produce proteins that mimic part of the coronavirus. The instructions stimulate the action of the immune system, turning the body into a vaccine factory that attacks viruses. Not real virus it is contained in vaccines.
Both the Pfizer / BioNTech and Moderna vaccines target the crown-shaped spikes on the surface of the coronavirus that it uses to penetrate healthy human cells. The spikes also give the virus family its distinctive name.
Vaccines appear to be just as effective. Pfizer and BioNTech’s vaccine was about 95% effective in preventing disease symptoms in their late-stage trial, while Moderna’s vaccine was about 94% effective.
Both are given in two doses; Pfizer 21 days apart and Moderna 28 days apart. Very few participants who received the vaccine in any of the trials became ill with Covid-19, and almost none became seriously ill.
The data that the companies have submitted to the Food and Drug Administration suggests they begin offering partial protection against Covid-19 around two weeks after recipients receive their first dose.
What is the difference between them?
Cold vs ultra cold
The main difference between the two vaccines is the temperature required to keep them stable in the long term.
Pfizer vaccine should be stored in extremely cold temperatures of minus 70 degrees Celsius (-94 Fahrenheit). Once thawed, it can only be refrigerated for 5 days. The vaccine requires a special shipping container filled with dry ice to keep it at the proper temperature.
Moderna’s vaccine can be stored at standard freezing temperatures of -20 Celsius (-4 Fahrenheit) for up to six months. After thawing, it can be stored in the refrigerator for up to 30 days.
Side effects and safety
Neither of the two large-scale clinical trials of the vaccines showed serious long-term side effects. But vaccines have slightly different short-term side effect profiles.
While the vaccines have not been compared head-to-head, Moderna’s vaccine appears to be associated with slightly more severe cases of fatigue, headache, and fever within a day or two after the second injection, especially in people younger than 65. .
Although it was not seen in their clinical trial, Pfizer’s vaccine has been linked to some cases of severe allergic reactions as it was rolled out in the United Kingdom and the United States. At least two health workers in Brittany and two in Alaska have reported serious allergic reactions shortly after receiving the Pfizer / BioNTech vaccine.
Britain’s medical regulator has said that anyone with a history of anaphylaxis or severe allergic reactions to a drug or food should not receive the Pfizer / BioNTech Covid-19 vaccine.
But the US Food and Drug Administration has said it should be safe for most Americans with allergies to get the vaccine.
Will masks still be needed?
More data is needed to understand exactly how effective either vaccine is in preventing transmission of the virus. While both are very effective in keeping symptoms and serious illnesses at bay, we don’t know if they prevent someone from getting infected. Until known, experts say, masks will continue to be needed to ensure vaccinated people do not transmit the virus.
Will Americans have a choice?
At this point, with a vaccine shortage, few people will be able to afford to express a preference for what to receive. The US Centers for Disease Control and Prevention has recommended that the first doses be given to healthcare workers and residents of long-term care facilities, and most states plan to do so.
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