The Centers for Disease Control addresses why some people might get COVID-19 after being vaccinated.
1. Do some individuals get COVID-19 although they've been fully-vaccinated?
COVID-19 vaccines are effective. However, a small percentage of people who are fully vaccinated will still get COVID-19 if they are exposed to the virus that causes it. These are called “vaccine breakthrough cases.” This means that while people who have been vaccinated are much less likely to get sick, it will still happen in some cases. It’s also possible that some fully-vaccinated people might have infections, but not have symptoms (asymptomatic infections). Experts continue to study how common these cases are.
2. What level of protection do the COVID-19 vaccinations provide?
Large-scale clinical studies found that COVID-19 vaccination prevented most people from getting COVID-19. Research also provides growing evidence that mRNA COVID-19 vaccines (Pfizer-BioNTech, Moderna) offer similar protection in real-world conditions. While these vaccines are effective, no vaccine prevents illness 100% of the time. For any vaccine, there are breakthrough cases.
3. What are other reasons why fully-vaccinated people might get COVID-19?
It’s possible a person could be infected just before or just after vaccination and still get sick. It typically takes about two weeks for the body to build protection after vaccination, so a person could get sick if the vaccine has not had enough time to provide protection.
New variants are spreading in the United States. Current data suggest that COVID-19 vaccines authorized for use in the United States offer protection against most variants. However, some variants might cause illness in some people after they are fully vaccinated.
4. Are COVID-19 symptoms less severe for those who develop COVID-19, even though they are fully-vaccinated?
There is some evidence that vaccination may make illness less severe in people who get vaccinated but still get sick. Despite this, some fully-vaccinated people will still be hospitalized and die. However, fully-vaccinated people are much less likely to be hospitalized or die than people with similar risk factors who are not vaccinated.
5. Is the CDC doing anything to watch for new patterns or trends in breakthrough cases?
CDC is working with state and local health departments to investigate COVID-19 vaccine breakthrough cases. The goal is to identify any unusual patterns, such as trends in age or sex, the vaccines involved, underlying health conditions, or which of the SARS-CoV-2 variants made these people sick. To date, no unusual patterns have been detected in the data CDC has received.
COVID-19 vaccines help protect people who are vaccinated from getting COVID-19 or getting severely ill from COVID-19, including reducing the risk of hospitalization and death. Studies show that fully-vaccinated people can be less likely to spread the virus to others, even if they do get COVID-19. CDC recommends you get a COVID-19 vaccine as soon as one is available to you. Fully-vaccinated people can resume activities that they did before the pandemic. If you haven’t been vaccinated yet, find a vaccine near you. Keep taking all precautions until you are fully-vaccinated.