Is the COVID-19 vaccine safe to take and does it have side effects?

COVID-19 / Sanitas Medical Center

Is the COVID-19 vaccine safe to take and does it have side effects?

Vaccines have played an important role in protecting the health and safety of communities and nations throughout history. The approved COVID-19 vaccines have undergone rigorous, multiple phased testing by the manufacturers as well as comprehensive evaluation by the FDA of the scientific data, manufacturing process and distribution techniques required. There is also ongoing safety monitoring and reporting.

According to the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA), adverse reactions are usually resolved within a few days and are mild to moderate in intensity. The most common adverse reactions reported after vaccination in clinical studies included: fever, nausea, muscle pain, headache, pain at injection site, and injection site swelling and redness. 


The two authorized COVID-19 vaccines at the moment are:

  1. Pfizer-BioNTech's COVID-19 vaccine:

This vaccine is recommended for people over 16 years old, and is given as an injection into the muscle on the upper arm. For this vaccine you should receive the second dose 3 to 6 weeks after the first one. In people without evidence of previous infection, the Pfizer-BioNTech vaccine was 95% effective based on evidence from clinical trials.

  1. Moderna's COVID-19 vaccine:

This vaccine is given as an injection into the muscle. It can be used in people 18 years of age and older. For this vaccine you should receive the second dose 4 to 6 weeks after the first one.  In general, after the second dose, the Moderna vaccine was 94.1% effective at preventing symptomatic Covid-19.


Is there one that is better than the other?

In terms of effectiveness, Pfizer-BioNTech's and Moderna’s covid vaccines have shown similar results in clinical trials. It is possible that in the future, as more mutations change the spike protein of the coronavirus and new variants become predominant, these vaccines might require some modifications to maintain their effectiveness. But based on the evidence so far, the new variants do not alter the effectiveness of these vaccines.


One-shot vaccine pending approval

Johnson & Johnson has a one-shot covid vaccine and is waiting for U.S. emergency use authorization. The efficacy rate was lower than Pfizer's or Moderna's. Pfizer and Moderna had mid-90s efficacy. J&J had an overall efficacy of 66 percent (with only one shot). J&J is also evaluating a two-shot regimen as well. The results for that will be available later this year.

When a vaccine requires two shots, the first shot helps your body recognize the virus and gets your immune system ready, while the second shot strengthens that immune response. This makes your body more prepared to fight infection. For instance, in the studies for Pfizer’s vaccine, the first shot seemed to be about 52% effective in preventing covid. The second shot increased that effectiveness to 95%. 


You still could get covid after the vaccine


After getting the first shot, it can take up to a few weeks for your body to develop the cells that will make you immune. This means that it’s possible for you to get sick (infected) during that time. So it’s important to continue wearing masks and practicing social distancing even after getting the vaccine.

Even after the second shot, there’s a chance that you could get COVID-19. But that chance is very low. What the 95% vaccine efficacy actually means is that vaccinated people had a 95% lower risk of getting COVID-19 compared with the control group participants, who weren't vaccinated. In other words, vaccinated people in the Pfizer clinical trial were 20 times less likely than the control group to get COVID-19.