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How Safe Is The Vaccine?

Millions of Americans have safely gotten vaccinated against COVID-19. However, because these vaccines are relatively new and the target of misinformation online, there may be apprehension about vaccine safety and efficacy.

We’ve asked our Yale New Haven Health experts to help clarify what we know about the vaccines and their current safety profiles.

What Do We Know About the Safety of the Available Vaccines?

All of the data that are available indicate that the Pfizer, Moderna and Johnson & Johnson vaccines are safe. The Pfizer vaccine, which was granted full approval by the FDA, consists of genetic material called mRNA, which stimulates the immune system to protect against the virus. The vaccine material breaks down quickly after it’s absorbed into cells and it does not impact our genes. The Moderna vaccine works in the same way.

The COVID-19 vaccines are new, but RNA vaccines have been around for the better part of the last decade. Experts have been researching this method to develop vaccines against other illnesses including influenza, Ebola and the Zika virus. Those years of scientific development helped researchers get to the point where we are today.

The Johnson & Johnson vaccine is different from the Pfizer and Moderna vaccines and only requires a single dose. 

While all of the COVID-19 vaccines are still being studied, it’s important to note that they had to be approved by the FDA before they were cleared for use. After a multi-step process to approve a vaccine, the FDA, along with the CDC, will continue to monitor the safety of COVID-19 vaccines to rapidly detect safety problems if they exist.

“Any time a new vaccine is presented to the FDA, it’s tested and reviewed thoroughly before approval, even if it’s for emergency use,” said Thomas Balcezak, MD, chief medical officer for Yale New Haven Health.

In addition to the FDA’s review, Connecticut’s governor has a vaccine advisory committee to review the data. The group, which includes Richard Martinello, MD, Medical Director of Infection Prevention for Yale New Haven Health, recommended the immediate distribution of the vaccine.

What Are The Side Effects?

Yale New Haven Health participated in the Pfizer vaccine trial, which included around 40,000 participants. During the course of that trial, no serious side effects were reported. Some mild side effects associated with the Pfizer vaccine can include a local reaction to the vaccination site, such as mild pain, redness or swelling. Similar side effects can occur with the Moderna and Johnson & Johnson vaccines as well.

Those mild reactions sometimes happen with other vaccines like the flu shot. To alleviate those minor symptoms, an ice pack can reduce soreness or swelling. A cool bath, drinking fluids and taking an over the counter pain reliever if approved by your doctor, could also be helpful. 

Other side effects can include fever, chills, fatigue, headache, muscle pain and joint pain. Some people get side effects from vaccines because they “tickle” the immune system, provoking a response. That just means the vaccine is working, and it’s not a reason to be alarmed. Because there is no live or dead virus in the vaccine, you cannot get COVID-19 from it.

As with any vaccine, there is a very remote chance that it can cause a severe allergic reaction, serious injury or death. Any time someone experiences emergency symptoms, such as trouble breathing, pain or pressure in the chest, confusion, bluish lips or face, or any other sudden and severe symptom, they should call 9-1-1.

How Effective Is The Vaccine?

The Pfizer vaccine is a 2-shot series given around three weeks apart. It is about 95% effective within one week of getting the second dose. It’s only around 53% effective after the first dose, which is why it’s important for all recipients to get the second dose. The Moderna vaccine has a similar efficacy, which is about the same as many common immunizations to protect against illnesses like polio and measles. A third dose of the Pfizer and Moderna vaccines are recommended for those with certain immunocompromising conditions. A booster of the Pfizer vaccine is recommended for certain individuals such as those 65 and older and those with certain underlying medical conditions. 

“This vaccine is safe and effective. The pandemic has taken a toll on everyone, but the availability of a vaccine with such an impressive efficacy is a testament to the researchers who have worked on this technology for years,” said Dr. Balcezak.

Johnson & Johnson found its vaccine was 72% effective in the U.S. and 66% effective overall in preventing severe cases, 28 days after vaccination.

Another COVID-19 vaccine by AstraZeneca is about 63% effective and uses a different technology than the Pfizer and Moderna vaccines. The World Health Organization granted emergency authorization for this vaccine, but it has not yet been approved for emergency use by the FDA in the U.S.

So far, the FDA predicts the Pfizer vaccine will be effective for several months and possibly a year. In the meantime, experts will continue to study the virus and the vaccines developed to fight it.

There may be some scenarios where some people may need to consult with their doctor before getting the vaccine. For example, anyone who is currently sick with COVID-19 or another respiratory illness should wait before getting it.

Learn more by visiting the CDC website