Yes, COVID-19 vaccines have a very strong safety record. The COVID-19 vaccines have been tested and monitored for safety more than any previous vaccine in U.S. history. All COVID-19 vaccines have been rigorously tested and reviewed for human safety through a three-phase clinical trial process.
More than 150,000 people participated in U.S. vaccine clinical trials, and almost 700 million vaccine doses have been safely administered in the U.S., with rare instances of adverse reactions. To ensure the continued safety of COVID-19 vaccines, data from clinical trials is collected and monitored for two years after each vaccine is first administered. Additional monitoring is in place for adverse event reporting through the Vaccine Adverse Event Reporting System (VAERS). Based on these thorough processes, public health officials make evidence-based recommendations to keep the public safe and healthy.
Yes, the COVID-19 vaccines are highly effective at reducing the risk of severe infection, symptomatic illness, hospitalization, and death. On average, the original Moderna, Pfizer-BioNTech, and Novavax COVID-19 vaccines were effective in preventing symptomatic COVID-19 illness by more than 85%.
A vaccine can only protect against a strain that it recognizes. As the virus continues to circulate and mutate over time, new variants are less recognizable to our immune systems. This leads to new infections — even for people who are vaccinated. As a result, updated vaccines have been developed to more closely target the currently circulating variants of concern and offer increased protection.
The updated Moderna, Pfizer-BioNTech, and Novavax vaccines that were approved in fall 2023 are critical to collective immunity. According to the latest research data, the newly updated COVID-19 vaccines are effective at producing strong immune responses to new variants, especially those originating from the Omicron variant. Individuals who received the updated COVID-19 vaccines have shown antibody responses that were almost 10 to 17 times higher against new variants than before they received the updated vaccine.
There are two key measures that determine vaccine effectiveness: clinical trial efficacy and real-world effectiveness.
Measuring vaccine effectiveness is a complex process. Oftentimes vaccine effectiveness data are not identical to vaccine efficacy data. This is because vaccine effectiveness takes into account the real world conditions in which vaccines are actually administered. Without context these statistics can oversimplify the number of factors used to determine outcomes. Vaccine effectiveness varies based on location, population, and specific health outcomes. The CDC and other public health researchers routinely monitor and evaluate data for vaccine effectiveness.
It’s true that COVID-19 vaccines were developed more quickly than most previous vaccines, but their development built upon many prior decades of work.
The process included the same rigorous safety reviews that are required for all new vaccines. Researchers were able to develop the vaccines quickly, safely, and effectively because the urgency of the pandemic created greater access to research funding, reduced bureaucratic obstacles, and encouraged unparalleled levels of government and industry cooperation.
As new variants appear, vaccine researchers will continue to update COVID-19 vaccines to provide the highest level of protection against the virus.
In general, you are considered “fully vaccinated” and up-to-date with COVID-19 guidelines after you have received the recommended doses of the updated vaccine for your age, health status, and vaccine history. Depending on these factors, being “fully vaccinated” can look different for each person. As science and the virus evolve, so does our understanding of what it means to be “fully vaccinated”. Researchers continue to watch closely for signs of waning vaccine immunity over time, monitor new variants of the virus, and track how data differs across groups.
If you are not sure if you are “fully vaccinated” consult with a healthcare provider about completing the primary vaccine series, getting at least one updated Pfizer-BioNTech or Moderna dose, or getting the updated Novavax series.
The risk of having a serious adverse reaction to the COVID-19 vaccine is very low—far lower than the risk of contracting COVID-19.
Severe adverse reactions after vaccination are extremely rare, but can cause long-term health issues. Rare adverse events – such as anaphylaxis and other allergic reactions, blood-clotting syndromes, heart inflammation, autoimmune diseases impacting the nervous system, and death – have been identified and investigated through the Vaccine Adverse Event Reporting System (VAERS).
Common reactions to COVID-19 vaccination include mild side effects, such as limb soreness, fatigue, low-grade fever, headaches, and chills. These reactions typically resolve within a few days.
COVID-19 vaccination is essential for everyone, including people who have already had COVID-19. Data show that recently sick people who do not get vaccinated at least two months after their recovery are more likely to get COVID-19 again than people who get vaccinated after their recovery. This means that the COVID-19 vaccines increase protection against each COVID-19 re-infection.
Although highly contagious variants have led to breakthrough infections among vaccinated people, being unvaccinated is a clear health risk. Immunity provided by the updated COVID-19 vaccines is more safe, robust, and consistent, when compared to immunity from COVID-19 infection. COVID-19 vaccination is the best way to protect against death, hospitalization, and long-term COVID-19 health consequences.
Vaccines, including the COVID-19 vaccines, cannot provide 100% or permanent immunity. But COVID-19 vaccines are extremely effective in preventing serious illness, hospitalization, and death. Given that COVID-19 is an evolving virus, researchers continue to monitor how long vaccines provide immunity, which groups may benefit from additional doses, and how well the vaccines protect against new variants of the virus.
“Breakthrough” COVID-19 infections refer to infections in people who have fully completed the recommended vaccination schedule. This type of infection is not uncommon and can occur for multiple reasons. When vaccinated, breakthrough infections typically lead to mild symptoms that do not require hospitalization. People who are not vaccinated continue to account for the vast majority of severe cases, hospitalizations, and deaths from COVID-19.
If you have questions about your risk of COVID-19, how to protect yourself, or the vaccines, consult with your healthcare provider.
On February 28, 2024, the CDC Advisory Committee on Immunization Practices (ACIP) updated its COVID-19 vaccine recommendations to reflect the latest research and clarify guidance.
What recommendations changed?
What recommendations have stayed the same?
What is a “booster”?: “Boosters” are additional vaccine doses that you get after receiving a primary vaccine dose to increase immune protection against that specific illness. The term vaccine “booster” has been used broadly in public health across many vaccines.
What is the difference between a vaccine “booster” and an updated vaccine? “Boosters” typically have the same formula as their primary vaccine dose, and they remind the immune system of what virus or bacteria to protect you against. Updated vaccines, like the annual flu vaccine, have formula changes compared to the original vaccine dose that increase its effectiveness against new circulating strains.
As research improves our understanding of COVID-19, health agencies are now recommending updated vaccines instead of boosters. People who got the original COVID-19 vaccine series needed a “booster” when the original strains were still dominant. Now that new substrains have become dominant, updated vaccines are needed to specifically target the new dominant strains and maintain protection from COVID-19.
Who can get “boosters”?: COVID-19 “boosters” are not available now that updated COVID-19 vaccines have been modified to target dominant virus strains. People who were previously eligible for a booster may now be eligible for an updated vaccine.
Who can get updated COVID-19 vaccines? Everyone should complete their age-appropriate, updated vaccine series. Updated Pfizer-BioNTech and Moderna vaccines are available for individuals as young as six months old. Updated Novavax vaccines are available for individuals age 12 and older. For the best protection this respiratory virus season, everyone should receive at least one dose of the updated vaccine.
It is safe to get any of the authorized and updated vaccines, regardless of whether your primary series or most recent dose was the Pfizer-BioNTech, Moderna, Novavax, or Janssen/Johnson & Johnson vaccine. However, for children age six months to four years old, the CDC recommends receiving the same brand as the entire primary series, if available.
When will updated vaccines be available? Updated COVID-19 vaccines should be available in your community by the end of December. The CDC recommends that everyone stay up-to-date on vaccinations by getting an updated vaccine dose at least two months after their last COVID-19 vaccination—either since their last dose, or since completing their primary series.
Yes, everyone age six months and older should get an updated COVID-19 vaccine at least two months after their last dose. This is also true for people who completed their primary series or received one or two “boosters”.
If you are recovering from a COVID-19 infection, you should consider delaying vaccination by three months from the start of your symptoms or positive test if you did not have symptoms. For specific guidance based on your health history, speak with your healthcare provider.
No, “boosters” were only given to fully vaccinated people. “Boosters” are no longer available and have been replaced with updated vaccines that target dominant virus strains.
The best way to protect yourself from getting severely ill from COVID-19 is to get vaccinated. The CDC recommends that unvaccinated people age six months and older get the updated primary series, and then wait at least two months to get their second or third updated Pfizer-BioNTech or Moderna vaccine dose.
Adults age 18 and older also have the option to receive an updated Novavax vaccine instead of an updated Pfizer-BioNTech or Moderna vaccine if they are unable to receive mRNA vaccines and haven’t previously received any other updated dose.
No, all COVID-19 vaccines have been effective at reducing the risk of severe illness. Getting a series of vaccine doses over an extended period of time – like months or years – is common for many vaccines. Healthcare providers recommend these vaccine series because over time the vaccine dose effect wanes and another dose is needed to restore optimal protection against new variants of a virus. The researchers who developed the COVID-19 vaccines continue to watch for waning immunity, how well the vaccines protect against new strains of the virus, and how that data differ across age groups and risk factors. This research has led to updated vaccines.
In the past, “boosters” have extended COVID-19 vaccine protection against serious illness, but they have been somewhat less effective in boosting immunity against new variants. The updated vaccine formula is designed to better target and protect against variants that currently account for most new infections.
The Novavax vaccine is a two-dose, protein-based COVID-19 vaccine. The vaccine is developed using more traditional protein-based technology compared to other available mRNA COVID-19 vaccines from Pfizer-BioNTech and Moderna. The Novavax vaccine uses a combination of purified coronavirus spike proteins and an immune-boosting stimulant called an adjuvant (common in many vaccines) to strengthen the body’s immune response against COVID-19.
On October 3, 2023, the CDC updated its COVID-19 vaccine recommendations, approving the updated Novavax vaccine for adults and children 12 years and older. It is the third COVID-19 vaccine available in the United States, in addition to Pfizer-BioNTech and Moderna vaccines. As a protein-based vaccine, Novavax is an option for people who are allergic to one of the components in a mRNA or viral-vector vaccine. Novavax is currently being used in more than 40 countries and has been authorized by the European Union and the World Health Organization.
On June 1, 2023, the Food and Drug Administration revoked its authorization and use of the Janssen (J&J/Janssen) COVID-19 vaccines in the United States. This authorization change was based on the latest data about the risk of developing a rare blood clotting disorder after receiving the J&J/Janssen vaccine. While the risk of a serious adverse reaction to the J&J/Janssen vaccine is very low and far lower than the risks for COVID-19 infection, it is higher than the other authorized vaccines.
Rare adverse events associated with Johnson & Johnson’s Janssen vaccine typically presented within days or weeks following vaccination. The risk of having an adverse reaction to the vaccine is very low, and even lower as time passes. The identification of any possible risks, like the risks associated with the J&J/Janssen vaccine, is a sign that the nation’s safety monitoring system for COVID-19 vaccines is working.
People who are not yet vaccinated, along with people who received the Johnson & Johnson vaccine and are eligible for an updated vaccine, should get a Pfizer-BioNTech, Moderna, or Novavax vaccine.
COVID-19 vaccines have prevented many deaths and hospitalizations, but the illness is still a public health risk. In 2022, COVID-19 was the fourth leading cause of death in the U.S. and is still a leading cause of severe illness and death, particularly for older adults and people who are immunocompromised. COVID-19 disproportionately impacts adults 65 years and older. More than half of COVID-19 hospitalizations from October to December 2023 occurred among people in this age group.
To protect this group and others with severe risk of illness, CDC health experts continue to recommend an additional dose of the updated COVID-19 vaccine to adults with compromised immune systems, especially those 65 years and older. This extra dose restores critical immune protection, which may have weakened since their last recommended dose.
In the same way that health experts track the flu and other common illnesses, these experts will continue to monitor COVID-19 and recommend measures to stay safe and healthy.
CDC continues to advise the public to practice precautions such as receiving updated COVID-19 vaccines, using at-home rapid antigen tests if you’ve been exposed and develop symptoms, staying home and isolating if you’re sick, and wearing a high-quality mask, as needed, when in public indoor areas.
Yes, your school or work can mandate the COVID-19 vaccine, with some exceptions. Schools or employers may require vaccinations for attendance or employment, and those requirements vary by state and employer.
While these requirements vary, the research remains the same: the best way to protect yourself from getting COVID-19 is to get vaccinated, and practice precautionary measures like handwashing, social distancing, wearing a mask, and isolating when sick.
Schools: All states have vaccination requirements for children attending school and childcare facilities. Vaccination requirements help safeguard children by making sure they are protected when they begin school, where there is a higher potential for transmission of some diseases. To learn more about vaccine requirements by state, visit the CDC’s SchoolVaxView Requirements Database.
Employers: On January 13, 2022, the Supreme Court ruled that the federal government cannot enforce a vaccine mandate for large businesses. This does not mean that private employers are blocked from creating vaccine mandates. Employers are still legally able to mandate COVID-19 vaccinations for employees.
Other Vaccine Requirements:
Yes, CDC recommends COVID-19 vaccination for all people who are pregnant, breastfeeding, or trying to get pregnant now or in the future. Data show that pregnant and recently pregnant people are more likely than non-pregnant people to get severely ill if they are infected with COVID-19, and highly contagious variants make it even more important to get vaccinated.
The American College of Obstetricians and Gynecologists and other leading health organizations are “strongly urging” anyone who is pregnant or planning to become pregnant to get vaccinated against COVID-19.
If you are pregnant, talk to your healthcare provider to learn more about COVID-19 vaccination.
No, a COVID-19 vaccine will not increase the risk of miscarriage. Studies show that miscarriages can occur in 11% to 22% of all typical pregnancies. There is no evidence that pregnancy risks or complications are increased because of COVID-19 vaccines.
Data do show that experiencing a COVID-19 infection during pregnancy increases the risk of delivering a preterm or stillborn infant. This is why vaccination is a critical layer of protection for the pregnant person and the infant. COVID-19 vaccination provides antibodies to the pregnant person and the baby, protecting them both from the increased risk of serious illness.
There has been extensive and ongoing safety monitoring of the COVID-19 vaccines, including analysis of vaccination before and during pregnancy. These studies specifically demonstrate that COVID-19 vaccination does not cause or relate to the occurrence of a miscarriage. To date, no monitoring system or other studies have identified any association between miscarriage and COVID-19 vaccination.
No, there is no evidence that fertility is impacted by any vaccine, including the COVID-19 vaccines.
Yes, data show that after receiving mRNA COVID-19 vaccines, pregnant people can pass on their antibodies to the child. These antibodies have been found in umbilical cord blood, which means that the placenta has transferred protective immune cells from the vaccinated person to the infant. They have also been found in breastmilk.
This transfer of antibodies to infants helps strengthen their vulnerable immune system when they’re too young for vaccination. In both of these cases, during pregnancy and while breastfeeding, more data are needed to determine how much protection these antibodies may provide to the baby.
A tech CEO posted a meme questioning what happened to all the “dangerous” COVID-19 variants. The heavily circulated image has been viewed over 69 million times. One post sharing the image claims that once mass COVID-19 vaccination ended, the virus stopped evolving, implying that officials only said variants were dangerous to get people vaccinated. Recommendation:
A popular social media post asks why the general public hadn’t heard of myocarditis prior to COVID-19 if the condition was “so normal.” Responses to the post insinuate that myocarditis was not an issue before COVID-19 vaccines and block users who point to evidence to the contrary. Recommendation: Medium Risk Sign Up for Public Health
A so-called “analysis” of CDC data falsely claims to have identified 780,000 reports of serious vaccine injuries during the COVID-19 vaccine rollout, including Bell’s Palsy, heart inflammation, miscarriages, and seizures. Vaccine opponents are circulating the false claim that 8 percent of COVID-19 vaccine recipients, or 18 million people, experienced adverse reactions so severe that they