Covid-19 vaccines Q&A
Questions and Answers about COVID-19 Vaccines
On this page, you will find answers to some of the most common questions people are asking about COVID-19 disease and vaccines. There is even more information available here.
How do mRNA vaccines work?
Scientists have been working on developing mRNA vaccines for over a decade. Over the years there have been several challenges. Scientists have now developed safe and effective vaccines that can be scaled up quickly. This ability to scale up production quickly is exactly what is needed during a pandemic.
The process of producing proteins in our cells is an amazing and complex process. People make mRNA all the time. The process starts with DNA, which carries our genetic code. DNA is present in the nucleus where it is transcribed to make mRNA. The mRNA travels to the cytoplasm where it binds to ribosomes, which function like little factories. Here the mRNA is translated into proteins that are needed for the cells to function.
mRNA vaccines take advantage of this machinery by specifically introducing the message to make the spike protein of the SARS-CoV-2 virus. That is the only message that the vaccines are carrying.
The mRNA is captured by immune cells called antigen presenting cells. These cells use the message from the mRNA to produce the spike protein which is then “expressed” or “exposed” on the surface of the cells. These immune cells now travel to a local lymph node. The spike protein is recognized as being foreign, and is “presented” to other cells of the immune system called B-cells and T-cells. The B-cells “see” the foreign spike protein and make antibodies against it. If we are later exposed to SARS-CoV-2 these antibodies will now recognize and attack the spike protein of SARS-CoV-2 and protect us from getting sick with COVID-19.
How well does the mRNA vaccine work?
More than 90% of people vaccinated during the clinical trials were protected from significant Covid-19 disease. This number may change as the vaccines are given to the general population. However, it is still expected that the vast majority of people who get the recommended vaccines, according to the time interval recommended, will be protected.
What are the side effects of the mRNA vaccine?
Side effects from both mRNA vaccines are caused as part of the immune response to the vaccines. In some ways, the more vigorous the immune response, the more common the side effects.
The most common side effects from the mRNA vaccines are:
In the clinical studies, Side effects occurred during the first week after vaccination, but were most likely one or two days after receipt of the vaccine. Side effects were more frequent following the second dose and more likely to be experienced by younger, rather than older, recipients. Although most people will not have significant side effects, some people may wish to schedule their vaccination, so that they will not need to call out of work the next day if they don’t feel well.
What ingredients are in the new mRNA vaccine?
The mRNA vaccines include:
mRNA – This mRNA is for the spike protein of SARS-CoV-2, the virus that causes COVID-19.
Lipids - These are molecules that are not able to dissolve in water. They protect the mRNA, so that it does not break down before it gets into our cells. These can be thought of as little “bubbles of fat,” which surround the mRNA like a protective wall. There are four different lipids in the Pfizer vaccine and three in the Moderna vaccine. One of the lipids in both vaccines is cholesterol. Theoretically, these lipids may be the most likely components of the vaccine to cause allergic reactions.
Salts and amines - The Pfizer vaccine contains four salts. One is table salt. The salts are used to keep the pH of the vaccine similar to that found in the body, so that the vaccine does not damage cells when it is administered. The Moderna vaccine also contains four chemicals to balance the pH, but two are in a class of organic compounds known as “amines” and two are acetic acid and its salt form, sodium acetate. Acetic acid is the main component of vinegar (other than water).
Sugar – This ingredient is literally the same as that which you put in your coffee or on your cereal. It is used in both of the vaccines to help keep the “bubbles of fat” from sticking to each other or to the sides of the vaccine vial.
These are the only ingredients in the mRNA vaccines.
The mRNA vaccines do not include any of the following:
Preservatives, like thimerosal
Who should NOT get the COVID-19 vaccine?
The Covid-19 vaccines have been extensively studied and millions of people have successfully received their first dose. When the COVID-19 vaccine becomes available to your priority group, you should get it, barring a few specific exceptions.
People who should NOT get the COVID-19 vaccine:
Anyone with a severe allergy (anaphylaxis) to a component of the COVID-19 vaccine.
Those younger than 16 years of age
People currently isolating or experiencing symptoms of COVID-19; these people can get vaccinated once they are finished isolation and their primary symptoms have resolved.
People who may get the vaccine after considering risks and benefits and/or consulting with their healthcare provider
People with certain immune-compromising conditions
People on anticoagulants
Individuals with a history of a severe allergy to any vaccine or injectable medication
People who should follow special procedures
Someone with a history of severe allergy (requiring medical intervention) to anything other than a vaccine or injectable medication can get the vaccine, but they should remain at the location for medical observation for 30 minutes after receipt of the vaccine.
Pregnant women who develop a fever after vaccination should take acetaminophen. (See more in the pregnancy-related questions lower on this page.)
People who recently had COVID-19 and were treated with antibody-based therapies (e.g., monoclonal antibodies or convalescent plasma) should wait until 90 days after treatment to be vaccinated.
People with a known COVID-19 exposure should wait until their quarantine is over before getting vaccinated (unless they live in a group setting, such as a nursing home, correctional facility, or homeless shelter, in which case they can be vaccinated during the quarantine period).
People who got another vaccine (non-COVID-19 vaccine) should wait at least 14 days before getting COVID-19 vaccine. Likewise, if a person got the COVID-19 vaccine, they should wait at least 14 days before getting any other vaccines (non-COVID-19 vaccines). You should not get allergy shots on the same day as your COVID-19 vaccine. That way in the rare event that you have a reaction you will know which injection was more likely to be the cause.
Is it safe to get the COVID-19 vaccine if I have COVID-19 and don’t know it?
The CDC does not recommend testing prior to vaccination because it would be very difficult to coordinate and there is no reason to suspect that there would be an issue. The Pfizer clinical trials included people who did or did not have COVID-19 previously and some people got the virus during the study. These situations did not present any issues of concern either.
Once I have been vaccinated against coronavirus, am I exempt from lockdown restrictions?
Everyone will still need to practice recommended public health measures because it will take time to slow or stop the spread of the virus. Two factors are important for understanding why:
While the vaccines appear to be highly effective at preventing disease, it might not prevent asymptomatic infection. An asymptomatic infection may occur when a person is exposed to the virus which still replicates in their body, but they don’t have symptoms because their immune system stifles the infection as a result of the vaccination. In this scenario, the person could potentially spread the virus without even knowing that they are infected. For this reason all vaccinated individuals should still continue practice physical distancing, hand washing and wearing a mask. The companies will be doing additional studies to better understand whether this is the case.
Scientists estimate that to control COVID-19, at least 70 to or 80 percent of the population will need to be immune from the SARS-CoV-2 virus. Given that the U.S. population is more than 330 million people, this means that almost 250 million of them will need to be immune to reach this goal.
Between March and November 2020, almost 12 million people in the U.S. were found to be infected, although estimates from antibody studies suggest that the number might be 3-7 times greater. Despite this the virus rages on, demonstrating just how many more people need to become immune before we can expect to control the spread of COVID-19. If we had to rely on infections alone to stop the spread of COVID-19, between 1 million and 5.4 million people would die on the way to 250 million people becoming immune.
For all of these reasons, there will still be some period of time during which other measures, such as masks, social distancing, and other public health measures, will be required to slow or stop the spread of the virus. And, because we won’t know who might still be able to be infected after vaccination or previous illness, everyone will be asked to comply.
Does a vaccinated person present a risk to unvaccinated family members in the same house?
The mRNA vaccines are not composed of live viruses, so there is no infectious virus to spread from a vaccinated person to someone else. But, we do not yet know if an a asymptomatic, vaccinated person can still transmit the virus. An asymptomatic infection may occur when a person is exposed to the virus which still replicates in their body, but they don’t have symptoms because their immune system stifles the infection as a result of the vaccination. In this scenario, the person could potentially spread the virus without even knowing that they are infected. For this reason all vaccinated individuals should still continue practice physical distancing, hand washing and wearing a mask.
Do the COVID-19 vaccines contain live virus?
None of the early vaccines (those by Moderna, Pfizer, AstraZeneca, or Johnson & Johnson) are live weakened versions (similar, for example, to the measles, mumps, rubella, or varicella (chickenpox) vaccines). Moderna’s and Pfizer’s are mRNA vaccines, and AstraZeneca’s and Johnson & Johnson’s are non-replicating vectored vaccines. You can learn more about the different types of vaccines being tested below in the response to “What types of COVID-19 vaccines are being tested?”
Can mRNA vaccines change the DNA of a person?
Since mRNA is active only in a cell’s cytoplasm and DNA is located in the nucleus, mRNA vaccines do not operate in the same cellular compartment that DNA is located.
Further, mRNA is quite unstable and remains in the cell cytoplasm for only a limited time. The mRNA never enters the nucleus where the DNA is located so it can’t alter DNA.
What types of COVID-19 vaccines are being tested?
Several approaches to COVID-19 vaccines are currently being tested. They include both tried-and-true as well as novel approaches.
Here is a brief summary of these different strategies:
Inactivated vaccine — The whole virus is killed with a chemical and used to make the vaccine. This is the same approach that is used to make the inactivated polio (shot), hepatitis A and rabies vaccines.
Subunit vaccine — A piece of the virus that is important for immunity, like the spike protein of COVID-19, is used to make the vaccine. This is the same approach that is used to make the hepatitis and human papillomavirus (HPV) vaccines.
Weakened, live viral vaccine — The virus is grown in the lab in cells different from those it infects in people. As the virus gets better at growing in the lab, it becomes less capable of reproducing in people. The weakened virus is then used to make the vaccine. When the weakened virus is given to people, it can reproduce enough to generate an immune response, but not enough to make the person sick. This is the same approach that is used to make the measles, mumps, rubella, chickenpox and one of the rotavirus vaccines.
Replicating viral vector vaccine — In this case, scientists take a virus that doesn’t cause disease in people (called a vector virus) and add a gene that codes for, in this case, the coronavirus spike protein. Genes are blueprints that tell cells how to make proteins. The spike protein of COVID-19 is important because it attaches the virus to cells. When the vaccine is given, the vector virus reproduces in cells and the immune system makes antibodies against its proteins, which now includes the COVID-19 spike protein. As a result, the antibodies directed against the spike protein will prevent COVID-19 from binding to cells, and, therefore, prevent infection. This is the same approach that was used to make the Ebola virus vaccine.
Non-replicating viral vector vaccine — Similar to replicating viral vector vaccines, a gene is inserted into a vector virus, but the vector virus does not reproduce in the vaccine recipient. Although the virus can’t make all of the proteins it needs to reproduce itself, it can make some proteins, including the COVID-19 spike protein. No currently licensed vaccines use this approach. AstraZeneca’s and Johnson & Johnson’s vaccines are non-replicating vectored vaccines
mRNA vaccine — In this approach, the vaccine contains messenger RNA, called mRNA. mRNA is processed in cells to make proteins. Once the proteins are produced, the immune system will make a response against them to create immunity. In this case, the protein produced is the COVID-19 spike protein. The Pfizer and Moderna COVID-19 vaccines use this approach.
DNA vaccine — The gene that codes for the COVID-19 spike protein is inserted into a small, circular piece of DNA, called a plasmid. The plasmids are then injected as the vaccine. No currently licensed vaccines use this approach.
Additional Covid 19 Vaccine Information here
Last Reviewed 1/18/2020