• A number of drug manufacturers are working on vaccines to protect us from the virus that causes COVID-19. Two of these, both mRNA vaccines, have been approved for use by the U.S. Food and Drug Administration (FDA):


    • Granted Emergency Use Authorization (EUA) status on December 18, 2020
    • Large-scale clinical trial of 30,000 participants with 94% efficacy
    • Requires 2 doses
    • Standard cold storage (-20° Celsius)
    • First shipments went to hospitals and pharmacies that serve long-term care facilities
    • Goal of 500 million to 1 billion doses worldwide in 2021


    • Granted Emergency Use Authorization (EUA) status on December 11, 2020
    • Large-scale clinical trial of 44,000 participants with 95% efficacy
    • Requires 2 doses
    • Ultra-cold storage (-70° Celsius)
    • First shipments went to hospitals with ultra-cold storage
    • Goal of 1.3 billion doses worldwide in 2021

    For updates, visit the COVID-19 Vaccination page from the Centers for Disease Control and Prevention (CDC).

  • The COVID-19 vaccines reduce the chance of infection, particularly severe infection requiring hospitalization, as well as reducing the chance of death. In addition, many of the serious, long-term effects of COVID-19 can be prevented, including:

    • cough
    • shortness of breath
    • chest pain
    • fatigue
    • joint and muscle pain
    • impaired thought and concentration, known as “brain fog”
    • headache
    • depression
    • problems with the heart, lungs, kidneys, nervous system, skin, and teeth
  • Los Angeles County’s vaccine distribution schedule is available here.

  • No. Neither of these currently available vaccines even contain the virus that causes COVID-19.

  • The COVID-19 vaccine is unlikely to result in a positive viral RNA test for active infection. But it should result in a positive serology test, which tests for antibodies to the spike protein found in SARS-CoV-2, because the vaccine works by teaching your body to create antibodies against this virus.

  • All of the important steps were followed. Each COVID-19 vaccine candidate in the United States must meet strict safety standards. Because of vast amounts of funding both from the U.S. government and large corporations, the following processes could be completed more quickly:

    • Enrollment in clinical trials: With recruiting staff scaled up, tens of thousands of participants could be recruited and enrolled in a short period of time.
    • Vaccine manufacturing: Extra funding allowed for a larger number of employees, warehouses, and manufacturing plants. In addition, the currently available mRNA vaccines could be manufactured more quickly than traditional vaccines because the actual virus did not have to be grown in the lab.
    • Vaccine distribution: Increased funding allowed for more and faster shipments of vaccine throughout the U.S. and around the world.
  • Both the Moderna and the Pfizer vaccines have been tested in large-scale clinical trials that included between 30,000 and 44,000 participants who were randomly assigned to two groups: one received the vaccine, while the other received a placebo. All participants then went about their normal lives to see which group fared better.

    Those who received the vaccines contracted COVID-19 at a rate of 5–6% of those in the placebo group, meaning that the vaccine is about 94–95% effective at preventing cases of COVID-19. In addition, the vaccines were also shown to be highly effective at preventing severe disease.

    Both vaccines require two doses, so their efficacy was measured after everyone received their second doses. In the Moderna study, the protection from the vaccine was measured two weeks after the second dose; with the Pfizer vaccine, protection was studied one week after the second dose.

    Here’s the data from the Phase 3 Pfizer trial of 44,000 participants:

      • 95% efficacy
      • All cases of COVID-19: 162 in placebo group vs. 8 in vaccine group
      • Severe cases: 9 in placebo group vs. 1 in vaccine group

    In the Phase 3 Moderna trial of 30,000 participants, the data look like this:

      • 94% efficacy
      • All cases of COVID-19: 185 in placebo group vs. 11 in vaccine group
      • Severe cases: 30 in placebo group vs. 0 in vaccine group
  • No—because the efficacy data was obtained one week after the second dose of the Pfizer vaccine, and two weeks after the second dose of the Moderna vaccine, we can’t assume any protection before that time. Also, any public health orders and other policies and protocols that are in place will continue to apply to both vaccinated and unvaccinated people. This disease is contagious, and we all have to work together to stay safe and healthy. And no vaccine is 100% effective—as long as there is COVID-19 in the population, there is still a chance that you could get COVID-19 (and spread it to others), even if you’ve had the vaccine. According to experts, as much as 70 to 85% of us must receive vaccines until we reach herd immunity and the pandemic ends.

  • Because both Moderna and Pfizer are two-dose vaccines, you have to get both doses to reach the 94–95% protection levels shown in the clinical trials. The schedules are different, though: there are 21 days between the two Pfizer doses, and 28 days between the two Moderna doses.

  • Remember: both of these vaccines were created as two-dose vaccines, and the clinical trials did not look at the level of protection one might have from just one dose. Take the Pfizer trial, for example—those who received the vaccine got one dose, and then the second dose 21 days later. That only gave researchers 21 days to glean any data about the effectiveness of the first dose—not really enough time to see the effect. Though it’s likely that there is some benefit from just one dose, there just isn’t enough data to tell us for sure. We also don’t know if any protection you may receive from the first shot will last over time, without that second shot to back it up.

    The data show that two shots are necessary to ensure the 94–95% efficacy, so you shouldn’t get the first shot unless you plan on getting the second. You should also understand that many people experience mild symptoms after each shot. This doesn’t mean that you are infected with COVID-19; rather, these symptoms show that your body is developing an immune response in case of future COVID-19 exposure. So, if you get these symptoms, it certainly doesn’t mean that you shouldn’t get the second dose—these symptoms are to be expected.

  • It’s important to try to get your second shot on time, as the efficacy data is based on a certain number of days between doses. That said, sometimes life gets in the way. These vaccines have a little extra time (up to 6 weeks) for that second dose, without it being considered late. And, even if it takes longer than that, you should still get the second shot.

  • Yes. Even though a prior infection with COVID-19 should offer some protection against future infection, we don’t know how strong that protection will be, or how long it will last. The vaccine is still important to achieve that 94–95% level of protection. Don’t get the vaccine while you have an active COVID-19 infection, but you should go ahead and get the vaccine as soon as you can once you’re well—as early as 10 days after you first showed symptoms. If vaccine supplies are short, you should have at least 90 days of protection from your COVID-19 infection to allow time for your vaccination. Remember, though, that you won’t have full protection from the vaccines until after you’ve received both doses.

    As the COVID-19 vaccine does not offer its full protection immediately, there will still be some who become infected between doses, or even after getting their second shot. That does not mean that the vaccine didn’t work—in fact, they may wind up with an even better immune response between their infection and the vaccine. Even so, it’s still vital to get both vaccine doses. The second shot may be received on schedule as long as you have been fever-free for at least 24 hours and you feel well. It’s fine to wait on the second dose until you meet those criteria—you’ll still gain the full protection even if the second shot is delayed a few weeks.

    If you received convalescent serum or monoclonal antibodies as part of your COVID-19 treatment, you should wait at least 90 days to get your vaccine, because these treatments could prevent your immune system from making its own antibodies against COVID-19.

  • Here’s what we know so far: the currently available COVID-19 vaccines are highly effective and result in a strong immune response. Often, when our bodies build an immune response due to a vaccine, we feel side effects similar to a mild case of the flu. The data from the COVID-19 vaccine clinical trials show:

    • With the Pfizer vaccine, 59% showed symptoms after the first dose, and 70% after the second dose. In the placebo group, 47% had symptoms after the first dose, and 34% after the second.

    The most common symptoms included fatigue, headache, muscle aches, chills, joint pain, and fever. About 4% had severe fatigue, and 2% had severe headache.

    • With the Moderna vaccine, 55% showed symptoms after the first dose, and 79% after the second dose. In the placebo group, 42% had symptoms after the first dose, and 37% after the second.
    • The most common symptoms included fatigue, headache, muscle aches, joint pain, and chills. Very few severe side effects were seen after the first dose; after the second dose, 11% experienced severe fatigue, 10% had severe muscle aches, 6% had severe joint pain, 5% had severe headache, and 2% had severe fever and/or chills.
  • Allergies are usually specific, so just because you have an allergy to a particular food or medication doesn’t mean you are more likely to be allergic to the COVID-19 vaccine. The only reason to not get the vaccine would be if you had a known allergy to the COVID-19 vaccine, or to any of its ingredients. Some people with egg allergies can’t get certain vaccines because they contain egg, but as mRNA vaccines are not made in chicken eggs, there is no additional risk to those with egg allergies.

    Those with many severe allergies should talk to their doctor first, and if you carry an EpiPen, you should bring it with you when you get your vaccination. Vaccine distribution centers in the United States are required to keep allergy medications handy in case of emergency, and the CDC recommends that each person who gets the vaccine stay under observation for 15 minutes (or half an hour for those with a history of severe allergic reactions). If you can’t wait the recommended amount of time, you should stay with other people (or on the phone with someone who knows where you are and that you were just vaccinated).