Vaccine frequently asked questions
Which vaccines have been approved for use in the US?
The Food and Drug Administration issued emergency use authorization (EUA) of a vaccine from Pfizer on December 11 and a vaccine from Moderna on December 18. In an emergency like a pandemic, if there’s evidence that strongly suggests that patients have benefited without serious side effects, then the FDA can decide it’s worth releasing a new vaccine or drug on an accelerated timeline. Current published and pre-publication data from the manufacturers of these two vaccines strongly indicate that both are safe and highly effective. As an additional safeguard scientists from California, Oregon, Nevada and Washington states reviewed all the data and confirmed that the Pfizer and Moderna vaccines are safe and effective (See Pfizer recommendation and Moderna recommendation.). As with all vaccines, even after release to the public the vaccines will continue to be studied and all adverse reactions, both mild and serious, will be carefully tracked and publicly reported. Find information about how clinical trials work on the CDC website.
When and where can I get a vaccine?
Because supplies are limited, vaccines will be offered under a multi-phased, multi-tiered system developed by the CDC and California’s public health agency, based on risk of exposure and serious illness. The first phase focuses on healthcare workers and residents of long-term care facilities. The second phase focuses on people 75 years of age or older and those considered "essential workers. Additional phases will follow as vaccine is available. It is not yet known when the general public will begin to be vaccinated, but it has been estimated to start in spring or summer. We will provide information as it becomes available. You can find more information about California’s guidelines online.
Are the vaccines safe?
There have been no reported serious safety concerns from the Pfizer and Moderna vaccines so far, and the CDC and the FDA will continue to monitor people who have received the vaccine to ensure there’s no evidence of even rare safety issues. The safety and efficacy of vaccines is reviewed by panels of independent experts retained by the companies, by FDA scientific staff, and by an independent panel of experts convened by the FDA. (See article on why Dr. Anthony Fauci thinks the vaccine is safe.) In addition, the state of California has collaborated with other western states to convene an additional scientific panel to independently review all the data before distributing any vaccine to California residents; this panel has also approved its use in the states involved.
We understand some of you might be nervous about the vaccine. We believe the risks from contracting the virus are greater than the possible risks from receiving the vaccine.
How effective are the vaccines?
Preliminary studies show that the Pfizer and Moderna vaccines are about 95% effective in protecting people against COVID-19 (meaning, 95 out of 100 people who received the vaccine did not become ill with COVID-19). Initial studies also show that for those few who did contract the virus, the cases were not severe. Pfizer results were published in the New England Journal of Medicine. Moderna’s Phase 3 results are available here.
Who should get a COVID vaccine?
The Pfizer vaccine is approved for everyone 16 years old or older and the Moderna vaccine is approved for everyone 18 and older. The only reason not to get the vaccine (contraindication) is a severe, potentially life-threatening reaction (anaphylaxis) to any vaccine component (see below). Those recommended to get the vaccine include people with:
- Underlying medical conditions of all varieties
- Autoimmune disease or who are on biologic agents that suppress the immune system
- A cancer diagnosis
Those who are severely immunocompromised may not mount as strong a response, but this in itself is not a contraindication to the vaccine and should be discussed with a healthcare provider.
What side effects do the vaccines have?
Most side effects are mild. They can include:
- Soreness at the site of the injection
- Feeling tired
- Feeling achy in muscles or joints
- Fever, chills
Vomiting and nausea have also been reported as a Moderna side effect.
Over-the-counter pain medication, such as Motrin and acetaminophen, can help with these side effects. These symptoms generally occur within 3 days of receiving the vaccine, may be more prominent after the second dose of the vaccine and generally resolve after 1-2 days. These signs and symptoms indicate that the immune response has been activated and the vaccine is working.
Can I get COVID-19 from the vaccines?
It is not possible to get COVID-19 from any of the vaccines currently in the pipeline. The Pfizer and Moderna vaccines use only a gene from the virus, while other vaccines being studied use inactivated virus. None of these can cause COVID-19. Also, you will not test positive for COVID-19 by the antigen or PCR test as a result of the vaccine.
If I am pregnant or breastfeeding, should I get the COVID vaccine?
The vaccines were not tested in pregnant or breastfeeding women, so there is no data specifically to address safety in this group. It is recommended that pregnant and breastfeeding women discuss vaccination with their healthcare providers. The American Academy of Pediatrics and American College of Obstetricians and Gynecologists both indicate that there is no theoretical safety risk with the vaccine, but emphasize that there are clear risks to pregnant women who contract COVID, including severe/critical respiratory failure and pre-term birth. Therefore, it is recommended that women consider specific risk of being exposed to the virus due to current local transmission and individual behavior and circumstance — including the level of exposure to COVID patients at work — and discuss vaccination with a healthcare provider. There is no known effect of the vaccine on lactation and it is not excreted in breast milk.
I heard that people had anaphylactic reactions to the Pfizer vaccine. What’s in the vaccine? Should I get the vaccine if I have a history of anaphylaxis?
None of the nearly 40,000 participants in the clinical trial experienced anaphylaxis, but two healthcare workers with a history of severe allergic reactions developed anaphylaxis after being vaccinated with the Pfizer product in the UK. Based on this, the CDC has recommended that people with anaphylactic reactions to other vaccines or injectable medications take extra precautions when getting the vaccine; those precautions will include the requirement for 30 minutes of observation in the vaccine clinic area following the injection (the requirement is 15 minutes of observation for everyone else). There is no precaution needed for those who have anaphylactic reactions to oral medications or things that are not medications like foods, pets, pollen, or latex.
Anyone who has experienced anaphylaxis in response to any of the Pfizer vaccine ingredients (listed below) should not get the Pfizer vaccine.
What are the ingredients in the Pfizer vaccine?
According to the U.S. Food and Drug Administration, the Pfizer vaccine includes:
- Active Ingredient
- nucleoside-modified messenger RNA (modRNA) encoding the viral spike glycoprotein (S) of SARS-CoV-2
- (4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis (ALC-3015)
- (2- hexyldecanoate),2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide (ALC-0159)
- Sometimes abbreviated as PEG, polyethylene glycol is one ingredient that some have experienced reactions to in other forms
- 1,2-distearoyl-snglycero-3-phosphocholine (DPSC)
- potassium chloride
- monobasic potassium phosphate
- sodium chloride
- basic sodium phosphate dihydrate
Note that the Pfizer vaccine does not contain preservatives.
Who should not get the Moderna COVID-19 vaccine?
A. You should not get the Moderna COVID-19 Vaccine if you:
- had a severe allergic reaction after a previous dose of this vaccine
- had a severe allergic reaction to any ingredient of this vaccine
Q. What are the ingredients in the Moderna vaccine?
A. The Moderna COVID-19 Vaccine contains the following ingredients: messenger ribonucleic acid (mRNA), lipids (SM-102, polyethylene glycol [PEG] 2000 dimyristoyl glycerol [DMG], cholesterol, and 1,2-distearoyl-sn-glycero-3-phosphocholine [DSPC]), tromethamine, tromethamine hydrochloride, acetic acid, sodium acetate, and sucrose.
Should I get the vaccine if I’ve recently received another vaccine such as flu or pneumonia?
You should wait 14 days and wait to receive any other vaccine for 14 days after your last COVID vaccine.
Do we know the long-term effects of the vaccines? How will long-term effects and rare side effects be tracked?
Although more than 70,000 people have been in the clinical trials for the first two vaccines, there is no long-term information because this virus and these vaccines are so new. There has been at least 2-3 months of follow up for people in the vaccine trials, and no serious side effects have been seen so far. With past vaccines, the vast majority of side effects become apparent within about 6 weeks after the last dose of the vaccine. The vaccine manufacturers will continue to monitor the people from the clinical trials and report more long-term data regularly to the public as it becomes available. As the vaccines are given to others outside of the trials, starting with healthcare workers as described above, those giving the vaccines will be required to report any and all adverse reactions to the CDC. This information will be shared with the public. In addition, the CDC will be using a text messaging system called “V-Safe” to actively check in with vaccine recipients at regular intervals, including daily check ins for the first week, for up to 12 months following vaccination to report any symptoms and reactions. V-safe After Vaccination Health Checker | CDC
How long will it take for the vaccine to start protecting me?
It will take 1-2 weeks after the second dose of vaccine to be considered “fully vaccinated” and have maximum protection.
How long will the vaccines be effective?
It is not known how long the vaccines will be effective in protecting against contracting COVID-19. Some medical experts, including Dr. Anthony Fauci, speculate they may be effective for more than a year.
How do the vaccines work?
COVID-19 vaccines help our bodies develop immunity to the virus that causes COVID-19 without having to get the illness. The body is left with a supply of “memory” T-lymphocytes as well as B-lymphocytes that will remember how to fight that virus in the future. You can learn more about the types of COVID-19 vaccines being developed and how they work on the CDC website. You can also learn about how the mRNA vaccines work in this article.
Do the Pfizer and Moderna vaccines interact with or modify my DNA in any way?
What are the differences between the Pfizer and Moderna vaccines?
Both vaccines are designed using a new approach to inject messenger RNA into muscle cells and have those cells produce the virus protein to which the immune system responds. There are differences in how the messenger RNAs are prepared and delivered, but the basic principles are the same. Both require two doses, 17-21 (Pfizer) or about 28 (Moderna) days apart.
Is one of the vaccines safer or better than the other?
At this time, there is no evidence to show that the Pfizer or Moderna vaccine is better or safer than the other. Both vaccines offer approximately 95% effectiveness after the 2 doses. Both had no evidence of serious adverse reactions in large-scale clinical trials.
Can I get dose 1 of Pfizer and then switch to Moderna (or vice versa)?
No. Both doses must come from the same manufacturer. The safety and efficacy of a mixed-product series have not been evaluated. If for any reason a mistake is made and mismatched doses are given, then it is recommended not to give a third dose but rather consider vaccination complete with the two doses. If for some reason it cannot be determined which product was given as a first dose or that product is no longer available, then a second dose of either mRNA vaccine may be given a minimum of 28 days later.