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How we know the COVID-19 vaccine is safe and effective
The arrival of the COVID-19 vaccine marked a big step toward getting back to the people and places we’ve missed for so long. But you may have heard different things about them from friends and family, social media, or the news. So, what are the facts? Here’s how we know the vaccine is safe and effective, according to medical experts.
The COVID-19 vaccine began rolling out less than a year into the pandemic. Vaccine development typically takes much longer, so it’s easy to wonder how we got this vaccine so soon. But the COVID-19 vaccine is held to the same safety standards as any other vaccine. Rigorous clinical trials have proven that they’re safe and effective.
The COVID-19 vaccine went through the same process as any other vaccine — only faster.
The public health emergency fast-tracked vaccine development
We knew early on that COVID-19 was extremely serious and spreading fast. The world needed a safe, effective vaccine as soon as possible. Here’s how we did it:
Scientists and medical experts around the world joined forces and shared resources. By working together, they developed the COVID-19 vaccine as quickly as possible.
The government spared no expense responding to COVID-19. A lot of money and resources went into making the vaccine, so more could get done in less time.
Finding volunteers for clinical trials is usually hard. But in this case, it was easy. When it came to COVID-19, people wanted to help. Researchers had a robust sample size almost immediately.
Because COVID-19 spreads so fast, we had a huge amount of data much faster than usual. It didn’t take long for researchers to prove the vaccine works.
Vaccine manufacturers don’t often start production until clinical trials are complete. But with the pandemic surging, they scaled up to make vaccines as soon as they got approved.
The COVID-19 vaccine is new, but the technology behind them is not. Research to develop new vaccines in case of a pandemic had been underway for decades. So, when the COVID-19 pandemic hit, scientists were well prepared. They put years of vaccine technology to work and tailored it to specifically fight the coronavirus.
Data proves the COVID-19 vaccine is safe and effective
The COVID-19 vaccine is among the safest, most effective vaccines ever. No vaccine is 100% effective — and they don’t need to be to save lives. Both the Pfizer and Moderna vaccines are more than 94% effective against COVID-19.1,2 And the Johnson & Johnson vaccine is shown to be 85% effective in preventing severe cases of COVID-19.3
For perspective, let's compare the COVID-19 vaccine to seasonal flu shots. Seasonal flu shots are only 40% to 60% effective. In the 2019–2020 flu season alone, they prevented about 6,300 people from dying. Flu shots also prevented around 7.52 million illnesses and 105,000 hospital stays.4
Now consider this: All 3 versions of the COVID-19 vaccine are more effective than a seasonal flu shot. Imagine how many illnesses, hospital stays, and deaths the COVID-19 vaccine will stop.
COVID-19 vaccine safety and effectiveness data is open to the public
All the data published by the Food and Drug Administration (FDA) is posted online and open for everyone to review. Below you can see how each version of the vaccine works — and why we know they’re safe:
COVID-19 vaccine side effects are usually minor and manageable
Like most vaccines, the COVID-19 vaccine can produce side effects. These side effects are normal signs that the body is building immunity. They may include:
- Pain at the injection site
- Fatigue
- Headache
- Muscle pain
- Chills
- Joint pain
- Fever
It’s important to remember that all vaccines carry risks for side effects. But these risks must be weighed against the benefits. COVID-19 is dangerous — anyone can develop life-threatening complications if they get it. The good news: The FDA and Centers for Disease Control and Prevention (CDC) confirmed that the benefits of the COVID-19 vaccine outweigh any risks for side effects.
Even though it’s extremely rare, allergic reactions can occur. Talk to your doctor before getting vaccinated if:
- You have a history of severe allergic reactions
- You carry an epinephrine injector (such as an EpiPen)5
- You have any questions or concerns about allergies or any other health conditions
Don’t get a vaccine with ingredients that have given you a severe allergic reaction in the past. If you find you’re allergic to a certain type of vaccine, do not get another dose of that vaccine.6
Visit the CDC website to learn more about the COVID-19 vaccine for people who have allergies. If you have questions or concerns about allergies or other health issues, talk to your doctor. Your doctor can help you decide if getting vaccinated is the right choice for you.
The COVID-19 vaccine doesn’t introduce the virus into your body. It only teaches your body how to recognize the coronavirus. This helps your body create antibodies to fight the virus in case you ever get it. Since no trace of coronavirus is in the vaccine, it's impossible to get COVID-19 from the vaccine.
The best thing you can do to protect yourself and your family from COVID-19 is to get vaccinated. And follow up with a booster as soon as you’re eligible. In addition to vaccination, you can keep everyone safe by:
- Wearing a mask indoors while in public
- Washing your hands often
- Getting a COVID-19 test at the first sign of symptoms
- Staying home when you're sick
Get the latest updates on the COVID-19 vaccine
Schedule an appointment. Get updates on booster shots. Learn how the vaccine works.
This article reflects the most current information available at the time of publishing.
1“Pfizer-BioNTech COVID-19 Vaccine Frequently Asked Questions,” Food and Drug Administration, fda.gov, accessed December 1, 2021.
2“Moderna COVID-19 Vaccine Frequently Asked Questions,” Food and Drug Administration, fda.gov, accessed December 1, 2021.
3“Janssen COVID-19 Vaccine Frequently Asked Questions,” Food and Drug Administration, fda.gov, accessed December 1, 2021.
4“Vaccine Effectiveness: How Well Do the Flu Vaccines Work?” Centers for Disease Control and Prevention, cdc.gov, accessed December 1, 2021.
5Kaiser Permanente does not endorse the medication mentioned. Any trade names listed are for easy identification only.
6“What to Do if You Had an Allergic Reaction After Getting a COVID-19 Vaccine,” Centers for Disease Control and Prevention, cdc.gov, accessed December 1, 2021.