As the Pfizer vaccine against COVID-19 begins to be administered across the nation this week, many of us have questions about the vaccine, its efficacy and what it means for how we continue to react to the pandemic. To answer some of those questions, we turned to Teena Chopra, M.D., professor of Medicine in the Division of Infectious Diseases at the Wayne State University School of Medicine, and corporate medical director of Hospital Epidemiology, Infection Prevention and Antibiotic Stewardship at the Detroit Medical Center and Wayne State University.

Dr. Chopra has become one of the key sources of COVID-19 information for Detroit and the nation during the pandemic, interviewed by countless newspapers, and radio and television stations. She also served on the Wayne State University Presidential Coronavirus Committee, assisting with preparations and response related to the virus.

When can I expect to have the vaccine available to me?

The U.S. Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices has set criteria to determine the priority of distribution of vaccination. When you specifically get a vaccine will depend on your age, underlying conditions and occupation, as outlined by the CDC.

If I have a choice, which vaccine should I get?

At this time, only the Pfizer vaccine has been granted approval by the Food and Drug Administration. Any vaccine approved by FDA should be considered safe for use. Early on, people will not have a choice as to which vaccine they can pick. They will get what is available. But as vaccine manufacturing and distribution picks up, most likely by the end of 2021, we may get to choose the vaccine we receive.

How effective are the vaccines?

Both the Pfizer and Moderna vaccines are 95% efficacious. Efficacy is a term that means how many cases of infections of a disease are prevented in the clinical trial. We have yet to find out if the vaccine helps in preventing disease transmission.

Should I be concerned about the speed with which these vaccines were developed and approved?

Even though the vaccines were developed and approved very quickly, we need to know that the mRNA technology used for the two vaccines (Pfizer and Moderna) has taken years of research and development. Also, we need to realize that the FDA and the pharmaceutical companies have not cut any corners to develop COVID-19 vaccines. The process of reviewing the safety and efficacy of the vaccine trials has been the same as with previous vaccines. The only difference is the process, which this time was concurrent rather than one after the other. For example, Phase 1and 2 trials have been conducted concurrent to Phase 3 trials, which sped up the process. This was possible because of an abundance of financial resources allocated to the COVID-19 vaccine development.

Will a vaccine solve everything?

A vaccine is not the answer but vaccination is! Vaccination acceptance by the community will help us achieve herd immunity or community immunity. However, it is too early to predict what percentage of the community has to be vaccinated before we can say herd immunity is achieved. It is advisable to achieve herd immunity through vaccination. This number is close to 80%, which will help slow transmission and gradually end the pandemic. We need to wait to evaluate if COVID vaccines prevent disease transmission, how long the immunity lasts and which type of people it will not work on before we can know that number.

Do both the Pfizer and Moderna vaccines require two injections?

Yes, both vaccines are a two-shot series. The second dose of the Pfizer vaccine is given after three weeks and the second dose of the Moderna vaccine should be administered after four weeks.

Why is a second injection necessary?

The second dose is very important as it boosts the immune response. If people don’t receive the second dose, the vaccine won’t be effective.

How long after the injection do the vaccine’s properties take effect in me?

Based on trials, the best protection will come seven days after the second dose, but there will be some level of protection about 12 days after the first injection.

Can someone get COVID-19 from the vaccine itself?

None of the COVID-19 vaccines in development contain the complete SARS-CoV-2 virus, so it is impossible for them to cause COVID-19.

After I’m vaccinated, can I still catch the virus?

No. The vaccine is very effective. There may be some people who get the vaccine but still may not be protected against infection. But we may not know who those people are. Hence it is even more important that we vaccinate as many people as possible to build up herd immunity.

After I’m vaccinated, can I be immune but still pass the virus to someone else?

We don’t know the answer to this question yet. We need to wait for additional studies to answer that.

How long will the vaccine last? Will I need boosters?

We don’t know that yet but based on the antibody response seen in the Pfizer and Moderna vaccines, which are both mRNA vaccines, it appears that it is unlikely we will need it every year. We need the flu vaccine every year because flu viruses change at a rapid rate. On the other hand, coronaviruses do change, but not with the same speed as flu viruses. We may need boosters, but they may not be annual.

What are some of the possible side effects after the injection? What should I watch for if I don’t have any allergies?

All vaccines can have some reactions and, rarely, side effects. Reactions include soreness redness and swelling at the site of the injection. Other reactions that were reported by some people who received COVID-19 vaccines during trials were fever, headache, nausea, muscle aches — all of which have been previously  reported with other vaccines.

These are not really side effects but reactions, which mean that the vaccine is doing what it is supposed to do — induce an immune response in our body. So, while these reactions may make you feel uncomfortable or even miserable for a couple of days, the good news is that your immune system is working.

Based on the Pfizer vaccine trials, 11% of younger people (12-15 years) were likely to report a fever as compared to only 1% of older adults (>= 55 years), which again points to the fact that as we get older our immune system responds less efficiently to threats.

Once I receive a vaccine, can I stop wearing a mask and practicing social distancing?

No, not at all. Vaccine is an added tool to our prevention tool box. We still need to mask, wash hands and socially distance. Remember, we still don’t know if vaccinated individuals can transmit the disease. It’s possible that when vaccinated individuals are exposed to the virus, it replicates within them and doesn’t cause the disease, but they can still spread to others.

Is the vaccine safe for my child?

The current vaccines were not tested and are not indicated for children. Trials in children are now beginning. Pfizer has begun testing in children 12 and older, and Moderna recently announced plans to test its vaccine in 3,000 teens. Hopefully, by the end of 2021, we will have a vaccine for children.