COVID-19 - Dr. Jim Halverson

Ask Dr. Halverson: Frequently asked questions about COVID-19 vaccines

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By Dr. Jim Halverson

Vaccination of local health care workers at high risk for contracting COVID-19 began last week in Ventura County.

Thank you to all who have been asking questions regarding the vaccines. Here are answers to several of the questions I have received.

How does an mRNA vaccine work?

The Pfizer and Moderna vaccines now available both use a piece of messenger RNA to facilitate immunity. Messenger-RNA carries a set of instructions that tells a cell to make a specific protein. For the novel coronavirus vaccine, this is the spike protein that is found on the surface of the viral envelope. The messenger RNA vaccine is able to enter our cells and instruct them to produce multiple copies of the spike protein. Once our cells make the spike protein, it is put on the surface of our cell, where it is seen by our immune system as a foreign protein. We then produce neutralizing antibodies to it. If we become infected with the virus, our neutralizing antibodies will bind to the virus and prevent it from entering our cells and causing disease.

The mRNA does not enter our cell’s DNA. It is not a full virus and cannot replicate itself. The mRNA is rapidly broken down by our cell once the instructions have been transmitted, so it does not cause any defects in our cells. 

Can mRNA vaccine cause COVID-19?

No. The vaccine is not a virus and cannot cause disease. Because it activates our immune system, it can cause mild symptoms in some people. Based on data from the clinical trials, the most common reactions to the vaccine are pain at the injection site, fatigue, headache, and muscle aches. These symptoms are  common with other vaccines as well, and are a sign that our body is responding to the vaccine and producing neutralizing antibodies.

Does the vaccine contain preservatives?

No. The vaccine does not contain preservatives, thimerosal or involve egg-based manufacturing. 

What is the difference between emergency use authorization and licensure (full approval by the Food and Drug Administration)?

Emergency use authorization is a process by which the FDA can authorize use of a medication or vaccine with less data when the benefits of the vaccine outweigh the risk. Emergency use authorization can only be issued during a declared emergency, such as the pandemic. Vaccines issued through an emergency use authorization will continue to be studied and have additional safety monitoring and informed consent and education associated with them. There were no skipped steps in the vaccine-manufacturing and approval process. The development and approval of these vaccines in just under a year are due to the remarkable effort of scientists, physicians, health care workers and volunteers who have stepped forward to help end this pandemic.

What does it cost to get the vaccine?

Any COVID-19 vaccine will be available at no cost to all of us.

How many doses are needed?

Both of the current vaccines require two doses. The Pfizer vaccine is given three weeks apart and the Moderna vaccine four  weeks apart. You will receive the same vaccine each time. 

How effective are the current vaccines?

Both vaccines reduced the number of COVID-19 infections by 95% in the vaccinated group versus the placebo group. This level of protection was achieved one week after receiving the second vaccination. Individuals who received one injection had approximately a 60% reduction in COVID-19 infections.

What are the side effects of the vaccines?

The most common reactions observed to date are pain at the injection site, fatigue, headache, and muscle aches. Less commonly observed are fever and nausea. These reactions typically subside in one to two days. The Centers for Disease Control and the FDA will continue to closely monitor for any adverse events or side effects as the vaccine is distributed to the public.

If I have allergies, can I get the vaccine?

Yes. Seasonal allergies and even food allergies, including allergies to shellfish, peanuts, or eggs, do not exclude you from getting the COVID-19 vaccine. Individuals who have had severe reactions, such as anaphylaxis, to injectable medication or vaccines in the past should not get the COVID-19 vaccine at this time pending further FDA review.

If I am vaccinated, can I still spread the virus to others?

The vaccine trials did not look at the vaccine’s ability to prevent virus transmission. We do know the vaccine is very effective at preventing illness in those receiving the vaccine. Because we are not yet aware of the ability to prevent viral transmission, it is important to continue to wear a mask and socially distance even after getting vaccinated.

Can I get the vaccine if I’ve already had COVID-19?

Yes, although there is not enough data currently to determine how prior infection with COVID-19 affects the efficacy of the vaccine. It is known that natural immunity to the virus wanes over time, so currently, under the emergency use authorization, individuals who have previously been infected are eligible to receive the vaccine.

How long does immunity last?

It is not known how long immunity will last from the vaccine. In the clinical trials that have been conducted to date, the median length of follow-up has been two months for vaccine recipients. It is also not known how long immunity from natural infection lasts. There are reports of waning antibody levels around three months after infection, and a few cases of reinfection have been reported. Research is ongoing with study participants.

Who cannot get the vaccine?

In the early phases of distribution, the vaccines will most likely be available for non-pregnant adults. Children and adolescents under age 16 in the Pfizer trial (and 18 in the Moderna trial) and pregnant individuals were not included in the first round of trials. 

As with other vaccines, anyone who has a fever or other symptoms of significant illness may not be able to get the vaccine until their symptoms resolve.

Will I receive the vaccine?

I received the first dose of the Pfizer vaccine Sunday morning, Dec. 20, at Ventura Community Memorial Hospital. I am very pleased that I have taken this important step to help bring the pandemic to an end. 

Stay properly informed, stay committed, stay positive, stay safe and stay well.


— Dr. Jim Halverson, a longtime Ojai physician, writes a weekly column on COVID-19 for the Ojai Valley News.

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