Feeling nervous about the COVID-19 vaccine? Here’s why it’s safe and effective

The COVID-19 vaccine is becoming more available across California

The COVID-19 vaccine is becoming more available across California. And we now have a third vaccine that has been authorized for FDA emergency use in the U.S. from Johnson & Johnson. While this might bring relief to some, others might be more hesitant to get the shot. Some people may have concerns about the vaccine’s safety and efficacy – or how effective it is. This might be due to how quickly the vaccines were developed. It might also be because the vaccines are new. Or, maybe some people are nervous about the potential side effects. 

It’s understandable to be concerned. But it’s important that as many people get vaccinated as possible. While some might be hesitant – especially those 18 to 24 years old – rest assured the new COVID-19 vaccines are safe and effective. And it is truly our best shot to finally help curb the pandemic. Below you will find responses to common concerns about the COVID-19 vaccines. This way you can be ready when the COVID-19 vaccine is available to you.

How were the COVID-19 vaccines developed so quickly? 

Normally, it might make sense that a vaccine takes many years to develop. But because of the pandemic, there was a worldwide collaboration to focus solely on understanding the virus that causes COVID-19. The entire genetic makeup (genome) of the virus was mapped and released in January 2020.  As a result, scientists had all the necessary resources they needed to make a vaccine. This included research, funding, production, trials, and approvals. Many steps were done in parallel – or at the same time – rather than one at a time. 

But that doesn’t mean that corners were cut. Researchers used the same rigorous standards for testing as they do for other vaccines. This includes multiple phases of clinical trials with large groups  and safety review. The phase III Moderna vaccine clinical trial included 30,420 people. The researchers followed the subjects an average of two months after the second injection. The Pfizer/BioNTech clinical trial included 43,448 people. Researchers also followed subjects for two months – in line with other vaccine trials. The Johnson & Johnson clinical trial included 43,783 people.

As of March 1, 2021, over 244 million doses of the vaccines have been administered worldwide. This number is only expected to increase. Side effects and safety in certain groups – for example, pregnancy and pediatric use – are still being studied.  

Are the COVID-19 vaccines safe?

In short, yes. Each vaccine went through three independent reviews to ensure safety. They were done by the FDA, CDC, and the Western states’ Scientific Safety Review Workgroup

One concern some people have is that the vaccines will give them COVID-19. This is not possible. Unlike some other earlier vaccines, the COVID-19 vaccines do not use a weakened ‘live’ virus to trigger an immune response. The Moderna and Pfizer BioNTech COVID-19 vaccines use mRNA technology. mRNA vaccines use messenger RNA to send information to immune cells to produce antibodies. These antibodies protect you from COVID-19. 

Some people fear that mRNA will change a person’s DNA. Again, this is not possible. mRNA is simply a messenger that tells immune cells to make a certain protein. It never enters the nucleus of the cell, where DNA is. And mRNA breaks down once the message is delivered. 

The Johnson & Johnson COVID-19 vaccine also sends information to immune cells to produce antibodies. But that vaccine uses double-stranded DNA technology to do the job. That does not integrate into a person’s DNA, either. Remember, we are all exposed to many common cold or flu viruses as well as bacteria daily. But they also cannot and do not change our DNA. 

People might also be concerned because mRNA and double-stranded DNA technology appear to be new for vaccine use. While this is the first time an mRNA or double-stranded DNA vaccine has received FDA emergency use authorization (EUA), this technology has been studied for decades. It has been researched for flu, Zika, rabies, and other viruses, as well as for targeting cancer cells. This is part of the reason why the vaccines were able to be developed so quickly. 

What about COVID-19 vaccine side effects?

While side effects might not feel good, they are a sign that the vaccine is doing its job. The immune cells are creating antibodies. These will help teach your body how to fight off the virus if you are exposed. Side effects also typically go away in a few days. And remember, there is no live virus in the vaccine. So side effects are not a result of getting infected with COVID-19. They are due to your body having an immune reaction related to developing the antibodies needed to fight infection. 

Common side effects of the COVID-19 vaccines are:
  • Pain and swelling at the site of injection
  • Fever
  • Chills
  • Headache
  • Tiredness

In very rare cases, people can have a severe allergic reaction to the shot. This is known as anaphylaxis. This is why everyone who gets the vaccine is monitored 15 to 30 minutes after getting the shot. Again, this is extremely rare. In fact, in the first 1,893,360 Pfizer-BioNTech doses given to people, there were only 21 cases of severe allergic reaction. For Moderna, only 10 cases of anaphylaxis occurred within the 4,041,396 doses given. For Johnson & Johnson, only one case of severe hypersensitivity was reported in the 21,895 people who received the vaccine in the U.S. clinical trial.

Millions of people have been safely vaccinated around the world. The CDC continues to gather side effect information (and sends reminders to people to get the second dose) using the v-safe app

Are the COVID-19 vaccines effective?

The COVID-19 vaccines are very effective. The Pfizer-BioNTech vaccine is 95% effective after getting the second dose. The Moderna vaccine is 94.1% effective after the second dose. The Johnson & Johnson vaccine is 85% effective at preventing severe disease after 28 days with only one shot – according to the U.S. study. Those numbers are quite high for vaccines. To give some perspective, flu shots are typically only 40 to 60% effective.  

There are many benefits to getting vaccinated. These include:
  • Reduced risk of getting COVID-19
  • Reduced risk of being hospitalized with COVID-19
  • Reduced risk of dying from COVID-19
  • Helping to build herd immunity

Getting vaccinated is one tool to help stop the pandemic. Even if you have recovered from COVID-19, you should still get vaccinated. That’s because scientists are still not sure how long post–COVID-19 immunity lasts, if at all. This means reinfection might be possible.

Keep in mind it’s still important to stay home if you’re sick, wear a mask, social distance, and wash your hands even after getting the COVID-19 vaccine. While you are less likely to get sick if you get the vaccine, you might be able to spread the virus to others. Also, new strains (mutations) are always developing as part of how viruses work. Data is still being collected on whether the vaccines will work against these new strains. So the more people follow public health mitigation strategies, the harder it is for the new strains to spread.  

The virus that causes COVID-19 is new for everyone. It can seem like information is changing all the time. Keeping up with the latest science can help you feel more assured as you face what you don’t know. But what you can be sure of is that the COVID-19 vaccines are safe and effective. Staying up to date via our COVID-19 resources page can help you make an informed decision that will keep you, your family, and your community safe.


Find out when the COVID-19 vaccine is available to you. Depending on where you live, you may be able to also set up an appointment. 

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