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The FDA recently approved the emergency use authorization for two COVID-19 vaccines, one from Pfizer and the other from Moderna.

What does “emergency use authorization,” or EUA, mean? An EUA can be issued during public health emergencies once it has been determined it meets certain statutory criteria and when the “known and potential benefits outweigh the known and potential risks,” according to the FDA.   

During Phase 1 of the clinical trials, the vaccine is given to a small number of healthy participants at increasing doses to gain information on the immune response and safety of the vaccine.

In Phase 2 trials, the vaccine is given to hundreds of people with differing health status and demographics, in varying dosages to find the lowest effective dose and to monitor for side effects.

Phase 3 entails testing the vaccine on thousands of participants, who are representative of the population the vaccine will be used on, in randomized controlled studies. This final phase helps determine the effectiveness and safety of the vaccine, compared to a control group, who receive a placebo.

An EUA can be given before Phase 3 of the trial is complete as long as data has been collected on adverse events for more than 3,000 participants representative of the general population, who have been followed for a median of two months after completion of the vaccine series. The FDA will continue to collect data by tracking adverse event submissions.

On Dec. 11, 2020, Pfizer was granted emergency use authorization for its COVID-19 vaccine on people who are 16 years of age and older. This vaccine is a two-part vaccine consisting of two shots given three weeks apart. It was determined to be 95% effective in preventing COVID-19 disease, but both doses are required for full protection.

Just like any vaccine, protection is not immediate, as it takes your body time to produce an immune response. A person will not be considered fully vaccinated until two weeks after the second dose. This vaccine does not contain a live virus, so it cannot give you COVID-19.

Some people have had some soreness at the injection site, fatigue, headache, fever, muscle or joint pain for a few days after receiving the vaccine, and these can occur after either the first or the second shot. Even if you experience these symptoms, it is important that you receive the second dose. This is just your body’s way of producing an immune response to the genetic material in the immunization.

On Dec. 18, 2020, Moderna received its EUA from the FDA. The Moderna vaccine was authorized for use in people 18 years and older. It consists of two doses given four weeks apart. It has similar side effects to the Pfizer vaccine. It has been found to be 94.1% effective in preventing COVID-19 approximately two weeks after getting the second dose.

Scientists are not sure what percentage of the population needs to be vaccinated in order to attain herd immunity; the more contagious the disease, the more people that will need to be vaccinated to achieve herd immunity.

Even if you have tested positive for COVID-19 in the past, it is important to get the vaccine since it is unknown if, or for how long, protection lasts after testing positive. You should defer getting the vaccine if you have a current infection of COVID-19 until acute symptoms and criteria for discontinuing isolation have been met.

For people who have received monoclonal antibodies or convalescent plasma as treatment, vaccine should be deferred for 90 days to avoid interference of the treatment with a vaccine-induced reaction, since there is no data on efficacy of vaccine on these patients.

There is not enough data on how effective the vaccines will be for immunocompromised people, as they might not have the ability to produce enough of an immune response to protect them from COVID-19.

If you are allergic to any of the ingredients in the vaccine, you should not get it. It is important that you get both doses by the same manufacturer since studies have not been done on the safety and efficacy of mixing the vaccines.

Given the limited information we have on these new vaccines and whether immunized people can still spread the virus, vaccinated people should continue to follow CDC guidelines to protect themselves and others. The distribution plan for the vaccine in South Carolina can be found at

Karen Balerna, RN BSN BCPA is a board-certified patient advocate and owner of Nurse Advocate Partners, serving Beaufort County. or