coronavirus vaccine

Coronavirus Vaccines: Here's What You Need to Know

Pfizer-BioNTech, Moderna, AstraZeneca-Oxford roll out vaccines to halt the spread of COVID-19 as numbers of deaths climb steadily

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The vaccination of Americans against the coronavirus has begun, with medical workers, politicians and senior citizens among the first to receive one of two vaccines that have gotten emergency approval in the United States: Pfizer-BioNTech and Moderna. A third vaccine, from AstraZeneca-Oxford, has won emergency approval in the United Kingdom, though results from its trials have raised questions about how effective it is. 

Here’s a look at who is producing the vaccines, how they work and how they differ.


Pfizer Inc., a New York-based drugmaker, paired up with the German company BioNTech to produce the first COVID-19 vaccine to get emergency use authorization from the Food and Drug Administration. The companies plan to seek full U.S. approval by April, Reuters reported.

Moderna, a much smaller biotech company based in Cambridge, Massachusetts, makes the second vaccine to receive emergency approval. It was developed with help from the National Institute of Allergy and Infectious Diseases. The company, founded in 2010 and whose name is short for modified RNA, had never gotten FDA approval for any of its vaccine candidates.

A third, approved in the U.K. on Dec. 30, is made by the U.K-based drugmaker AstraZeneca, in collaboration with the University of Oxford. It needs only normal refrigeration, making it easier to distribute around the world, and it is the first to have its trial results published in a peer-reviewed medical journal, The Lancet.

Less is known about two other vaccines, the Russian-made Sputnik V, the first to be released, and the Chinese-made Sinopharm. Russia has been criticized for approving the vaccine on Aug. 11 before late-stage testing to ensure its effectiveness and safety was complete. Sinopharm has released findings with minimal details, The New York Times reported, and Chinese regulators have not approved it or other vaccines in the pipeline. There has been little information on whether the vaccines are effective.

Colorado Gov. Jared Polis provided more details Wednesday about the first person in the U.S. to test positive for the highly contagious coronavirus variant first identified in the U.K. Polis warned that while this is the first case confirmed by a lab test, there were likely earlier cases in the U.S. that had not been identified.


Like other vaccines, the ones designed to protect you from COVID-19 prompt your immune system to produce antibodies, just as if you had been exposed to the virus. 

How the Pfizer-BioNTech and Moderna vaccines differ from traditional vaccines is in their use of mRNA. Instead of introducing a weakened or an inactivated germ into your body, this vaccine injects mRNA, the genetic material that our cells read to make proteins, into your upper arm muscle. It teaches your body how to make the protein that triggers antibody production so if the real virus later enters your body, your immune system will recognize it, according to the federal Centers for Disease Control and Prevention. 

The AstraZeneca vaccine also relies on instructions for creating the spike protein that gives the coronavirus its distinctive shape and which it uses to enter a cell. The AstraZeneca vaccine is different from the other two because it makes use of DNA inside an adenovirus, a common virus. 

Congressman-elect Luke Letlow, R-La., has died from complications of the coronavirus at the age of 41.


The mRNA vaccines contain instructions for the distinctive spike protein found on the surface of the coronavirus and which attaches to a particular protein in our body. Once the mRNA is inside your muscle cells, the cells translate the genetic information to make the protein or antigens and display it on their surface, according to Pfizer. Your immune system spots the antigens, recognizes it as foreign and begins to make antibodies. 

One key difference between the Pfizer-BioNTech and Moderna vaccines is how they are stored. The Pfizer BioNTech one must be stored at minus 94 degrees Fahrenheit or colder, while Moderna’s can remain at regular refrigeration temperatures of between 36 degree and 46 degrees Fahrenheit for 30 days. 

Paula Cannon, an associate professor of microbiology at the University of Southern California's Keck School of Medicine, told NBC News that the difference was likely due to the way the vaccine’s synthetic mRNA was packaged. The molecule is fragile and is kept stable with a protective fatty covering.

Vice President-elect Kamala Harris received her first dose of the Moderna coronavirus vaccine on Tuesday morning.

The AstraZeneca vaccine uses a modified version of a chimpanzee adenovirus, which once injected into your arm inserts its DNA into a cell’s nucleus. The cell in turn sends messenger RNA or mRNA out of the nucleus with instructions for making spike proteins, which activate your immune system. The DNA is more stable than the mRNA on which the Pfizer-BioNTech and Moderna vaccines are based and does not need to stay frozen. That is key to its potential as a “vaccine for the world.” It needs only normal refrigeration and so can be easily distributed.


The CDC notes that none of the vaccines uses the live virus that causes COVID-19. The Pfizer mRNA vaccine for example contains instructions for making a harmless piece of just one of the coronavirus' 29 proteins and your body breaks down those instructions and gets rid of them once it has made the spike protein.


The Pfizer BioNTech vaccine is 95% effective according to results of its late-stage trial announced in November, surprising some people. In August, Dr. Anthony Fauci, the White House coronavirus advisor, said that scientists were hoping for a vaccine that was at least 75% effective, but that 50% or 60% would also be acceptable. The vaccine is given in two injections, 21 days apart, but provides strong protection within about 10 days of the first one. 

The Moderna vaccine provides a similar level of protection, 94.1%. It also requires two shots, 28 days apart. It is not known if either prevents the spread of the virus by people who are asymptomatic.

The AstraZeneca vaccine protected against the diseases in 62% of the people who got the two doses but in 90% of those who got only one in error, though that group is too small to be conclusive. That gave an average effectiveness of 70% effective, though its developers expect it to be as effective as the others. The doses are to be administered in an interval of between four and 12 weeks, although because of the upsurge of cases in the U.K., public officials are prioritizing giving as many people as possible the first dose.

British officials are investigating reports that two people who received the Pfizer vaccine had allergic reactions. Medical experts say that while reactions are rare, they aren’t unheard of for vaccines of any kind and are usually short-lived.


The Pfizer-BioNTech and Moderna vaccines are considered by American regulators to safe and effective, according to the findings of the large clinical trials.

U.K. regulators say the AstraZeneca vaccine also is safe and effective.

There were reports of serious allergic reactions during the rollout of the Pfizer vaccine in the U.K. People there were advised not to get the COVID-19 vaccine while medical officials investigate whether two reactions on the first day of the vaccination program there were linked to the shot. A doctor in Boston with a shellfish allergy had a serious reaction to Moderna's vaccine, used his allergy auto-injector and was later discharged from Boston Medical Center, health officials reported.

Experts say that allergic reactions are not unexpected with vaccines, but that they are usually rare and short-lived. In the Pfizer-BioNTech study, the rate was about the same in those who got the coronavirus vaccine versus those who got a dummy shot, 0.63% versus 0.51%. 

The AstraZeneca vaccine trial was halted after a volunteer developed symptoms of a neurological disorder, but it resumed after the symptoms were shown to be unrelated to the vaccine. 


The Pfizer shot could cause flu-like side effects that include sore arms, muscle aches, fever, fatigue, headaches and joint pain. Study results indicated most of these symptoms cleared up between one to three days after beginning.

Moderna’s side effects were similar, according to the FDA: pain where the injection was given, tiredness, headaches, muscle pains, chills, joint pains, swollen lymph nodes in the same arm as the injection, nausea and vomiting, and a fever. They typically lasted several days. 

Clinical results for the AstraZeneca vaccine published in The Lancet recorded mild to moderate side effects similar to mild side effects from the Pfizer-BioNTech vaccine. 

Colorado Governor Jared Polis said Tuesday the COVID-19 variant first detected in the United Kingdom had been detected in Colorado. U.K. scientists believe the variant is more contagious than previous strains of the virus.


AstraZeneca made a series of blunders that left U.S. regulators wary about the results of its trials, according to reports in The New York Times and The Wall Street Journal. The Wall Street Journal reported that the company expects to have data from a clinical trial in the United States in February that it can show the FDA. 


Scientists were able to develop the mRNA vaccines for coronavirus so quickly because mRNA vaccines have been studied before for flu, Zika, rabies, and cytomegalovirus or CMV, according to the CDC. In 2019, BioNTech made a cancer vaccine that was administered to people with advanced stage melanoma and that matched the genetic profile of each individual cancer.

Similarly other vaccines based on adenoviruses are in the works. One for Ebola that is made by Johnson & Johnson was approved in July. Clinical trials are ongoing for Zika and H.I.V.

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