Warning: People Vaccinated Against COVID-19 May Still Get Infected — What You Need to Know
COVID-19 vaccination has changed the course of the pandemic by providing strong protection against the most serious consequences of infection. However, vaccination does not mean that a person can never become infected with SARS-CoV-2, the virus that causes COVID-19.
People who have received a COVID-19 vaccine may still test positive, develop symptoms, or transmit the virus to another person if they become infected. These infections are commonly referred to as breakthrough infections.
This fact should not be interpreted as meaning that COVID-19 vaccines are ineffective. Rather, it highlights an important principle of modern vaccination: protection against severe disease can remain strong even when protection against infection is incomplete.
As of 2026, the World Health Organization continues to state that COVID-19 vaccines provide protection against severe disease and death, while acknowledging that vaccinated people can still become infected.
What Does “Breakthrough Infection” Mean?
A breakthrough infection occurs when a vaccinated person becomes infected with SARS-CoV-2.
Vaccines prepare the immune system to recognize and respond to a virus. They do not necessarily prevent the virus from entering the nose, throat or respiratory tract in every situation.
Consequently, a vaccinated person can occasionally become infected even after receiving the recommended vaccination.
The WHO explains that COVID-19 vaccines are highly effective at preventing serious disease and death, but no vaccine is 100% effective. Breakthrough infections therefore remain possible.
This distinction is important because people sometimes expect vaccination to provide complete protection against infection. In reality, vaccines can provide different levels of protection against:
Infection
Symptomatic illness
Severe disease
Hospitalization
Death
Transmission to other people
Protection against these outcomes is not necessarily identical.
Can Vaccinated People Still Get COVID-19?
Yes.
A vaccinated person can still develop COVID-19. However, vaccination generally provides much stronger protection against severe outcomes than against infection itself.
According to the WHO's current information, people who develop COVID-19 after vaccination are more likely to experience mild illness because protection against serious disease and death remains high.
This means that a positive COVID-19 test in a vaccinated person does not automatically indicate that the vaccine has failed.
For example, consider two people exposed to the same variant of SARS-CoV-2. One is vaccinated and the other has no vaccine-derived protection. Both could potentially become infected, but their immune responses and risks of serious illness may be different.
Vaccination essentially gives the immune system a head start.
Why Doesn't Vaccination Prevent Every Infection?
Viruses that primarily infect the respiratory tract can be particularly difficult to block completely.
SARS-CoV-2 can enter through the nose or mouth and begin replicating in the upper respiratory tract. Immunity may reduce the ability of the virus to establish an infection or progress to serious disease, but it does not guarantee that viral particles can never enter the body.
There is another important factor: immunity changes over time.
The WHO reports that protection against severe disease and death is highest during the first few months following vaccination and then decreases. Immunity can also decline relatively quickly after vaccination or infection, which is one reason periodic vaccination may be recommended for people at higher risk.
The circulating virus also changes.
SARS-CoV-2 has produced numerous variants and subvariants since the beginning of the pandemic. Updated vaccines are designed to maintain useful protection as the virus evolves, although protection against infection can vary depending on the match between the vaccine and circulating viruses.
Vaccination Still Matters
The possibility of breakthrough infection should not obscure the principal purpose of COVID-19 vaccination.
According to WHO, COVID-19 vaccines continue to provide protection against severe disease and death. WHO's current recommendations focus particularly on people at higher risk of severe COVID-19.
This is an important distinction.
A vaccine does not necessarily have to prevent every infection to provide major health benefits. Reducing the likelihood that an infection becomes severe can itself prevent hospitalizations, intensive medical care and deaths.
WHO also reports that COVID-19 vaccines have saved millions of lives worldwide by reducing severe disease, hospitalization and death.
Can Vaccinated People Transmit COVID-19?
Yes.
If a vaccinated person becomes infected, they may be able to transmit SARS-CoV-2 to other people.
Vaccination can reduce the likelihood and duration of some infections and can reduce the severity of illness, but it should not be treated as a guarantee that an infected vaccinated person cannot spread the virus.
WHO specifically notes that it remains possible for someone to spread COVID-19 after becoming infected despite vaccination.
This is particularly relevant when a vaccinated person develops symptoms or has a known exposure.
If you have symptoms consistent with COVID-19, following applicable local public-health guidance and taking reasonable precautions around vulnerable people can help reduce the chance of transmitting respiratory viruses.
What Symptoms Can Vaccinated People Experience?
A breakthrough infection can produce symptoms similar to those associated with COVID-19 generally.
Symptoms can include:
Sore throat
Cough
Runny or blocked nose
Fatigue
Headache
Fever
Muscle aches
Loss or change of taste or smell
Shortness of breath
Other respiratory symptoms
The exact symptoms can vary according to the individual and the virus variant circulating at the time.
Vaccinated people who become infected may experience mild symptoms, and some may have no noticeable symptoms at all.
However, vaccination does not make serious illness impossible. Older adults and people with certain underlying medical conditions or weakened immune systems can remain at increased risk.
Who Remains at Higher Risk?
COVID-19 does not affect every person in the same way.
Risk of severe disease can be higher among older adults and people with certain medical conditions or immune-system problems. WHO's current recommendations therefore place particular emphasis on vaccination for groups at highest risk of severe COVID-19.
The exact vaccination schedule can vary between countries and according to age, health status, previous vaccination and infection history.
For that reason, people should consult current guidance from their national health authority or healthcare professional rather than relying on an old vaccination schedule from the early stages of the pandemic.
Does a COVID-19 Vaccine Cause COVID-19?
COVID-19 vaccines do not cause COVID-19 in the way an infection with SARS-CoV-2 does.
Different COVID-19 vaccines use different technologies. WHO currently describes both protein-based vaccines and mRNA vaccines among the types being manufactured.
An mRNA vaccine, for example, uses genetic instructions that enable cells to produce a harmless piece of viral protein temporarily. This helps the immune system recognize the virus.
The vaccine does not need to give a person a live SARS-CoV-2 infection in order to stimulate immunity.
It is therefore important to distinguish between symptoms that can occur after vaccination and symptoms caused by an actual COVID-19 infection.
What Side Effects Can Occur After Vaccination?
COVID-19 vaccines can cause side effects, as can many other vaccines and medicines.
The U.S. Centers for Disease Control and Prevention (CDC) lists common short-term reactions including:
Pain, soreness or redness at the injection site
Fatigue
Headache
Muscle pain
Joint pain
Chills
Fever
Nausea or vomiting with some vaccines
These reactions are generally mild and temporary.
Experiencing a short-term reaction does not mean that someone has developed COVID-19.
The CDC also emphasizes that adverse events following vaccination are rare, although serious events can occur and continue to be monitored.
What About Serious Vaccine Reactions?
Like other medical products, COVID-19 vaccines can have rare serious adverse reactions.
One example is anaphylaxis, a severe allergic reaction. The CDC describes anaphylaxis after COVID-19 vaccination as rare and notes that it requires immediate medical treatment.
Another rare adverse event associated with some COVID-19 vaccines is myocarditis or pericarditis, which involve inflammation of the heart muscle or surrounding tissue.
The CDC states that these conditions have been observed rarely following COVID-19 vaccination and have occurred most frequently in adolescent and young adult males, although cases have also occurred in other groups.
Anyone experiencing concerning symptoms after vaccination should seek appropriate medical advice.
In particular, the CDC advises seeking medical attention promptly if chest pain, shortness of breath or a feeling of a rapidly beating, fluttering or pounding heart develops after COVID-19 vaccination.
How Can You Tell the Difference Between Vaccine Side Effects and COVID-19?
Timing can provide a clue, but it is not always possible to determine the cause based only on symptoms.
Typical vaccine reactions generally begin shortly after vaccination and resolve within a few days. The CDC describes common post-vaccination side effects as mild and temporary.
An actual COVID-19 infection, on the other hand, occurs after exposure to SARS-CoV-2.
If someone develops symptoms after a possible exposure, testing may be appropriate depending on current public-health recommendations and the person's circumstances.
People who are at increased risk of severe disease should seek medical advice promptly if they develop COVID-19 symptoms because some treatments work best when started early.
Does a Positive Test Mean the Vaccine Did Not Work?
No.
A positive test indicates that a person was infected with SARS-CoV-2. It does not, by itself, tell us whether vaccination has provided protection against severe disease.
This is one of the most important points to understand when discussing breakthrough infections.
Suppose a vaccine reduces the probability of severe disease substantially but does not completely prevent infection. A vaccinated person could still test positive while benefiting from protection against hospitalization or death.
WHO explicitly states that breakthrough infections do not mean that COVID-19 vaccines do not work.
Why Does Protection Change Over Time?
The immune response is not static.
After vaccination, the immune system develops defenses against the virus. Over time, some components of that immune response decline.
WHO reports that protection against severe disease and death is highest in the first few months following vaccination and subsequently decreases. It also notes that immunity declines relatively quickly within approximately six months after vaccination or infection.
This does not mean that immunity suddenly disappears.
Instead, protection changes gradually, and the level of protection can differ depending on the outcome being considered.
Protection against severe disease may remain stronger than protection against infection.
Why Are Updated Vaccines Used?
SARS-CoV-2 continues to evolve.
As the virus changes, the immune response generated by an older vaccine may not match circulating variants as closely as an updated formulation.
WHO's 2026 position paper addresses vaccination in the context of continued SARS-CoV-2 circulation, high levels of population immunity and the availability of variant-adapted vaccines.
The goal of updating vaccines is to maintain meaningful protection against currently circulating viruses, particularly against serious outcomes.
The exact vaccines and recommended schedules differ between countries.
Should Vaccinated People Still Take Precautions?
Vaccination is an important layer of protection, but it is not the only possible measure.
If someone is sick with a respiratory infection, staying away from vulnerable people when possible, improving indoor ventilation, practicing good respiratory hygiene and following current local health guidance can help reduce transmission.
Additional precautions can be particularly important around people who are older, immunocompromised or otherwise at higher risk of severe COVID-19.
The appropriate precautions can also depend on the level of COVID-19 activity in the community and the individual's circumstances.
What Should You Do If You Think You Have COVID-19?
If you develop symptoms after a possible exposure, consider testing according to current local recommendations.
If your test is positive, follow current public-health guidance concerning staying home, returning to normal activities and reducing contact with others.
If you are at higher risk of severe COVID-19, contact a healthcare professional promptly. Treatment decisions may depend on factors such as age, medical history, immune status and how long ago symptoms began.
Seek urgent medical attention for severe symptoms such as significant difficulty breathing, persistent chest pain, new confusion, inability to stay awake or other signs of a medical emergency.
Common Misunderstandings About COVID-19 Vaccination
Myth 1: “Vaccinated people cannot get COVID-19.”
Fact: Vaccinated people can still become infected. WHO describes these as breakthrough infections.
Myth 2: “A breakthrough infection proves that the vaccine does not work.”
Fact: Vaccine effectiveness should be evaluated according to the outcome being measured. COVID-19 vaccines provide their strongest and most important protection against severe disease and death.
Myth 3: “Vaccinated people cannot transmit the virus.”
Fact: If a vaccinated person becomes infected, they can still transmit SARS-CoV-2.
Myth 4: “No symptoms after vaccination means the vaccine did not work.”
Fact: Vaccine side effects are not a reliable measurement of immune protection. Some people have few or no noticeable side effects while still developing an immune response.
Myth 5: “Every health problem occurring after vaccination was caused by the vaccine.”
Fact: A health event that occurs after vaccination is not automatically caused by vaccination. The CDC distinguishes an adverse event occurring after vaccination from an event proven to have been caused by the vaccine.
The Bottom Line
The warning that people vaccinated against COVID-19 may still become infected is true.
However, this fact needs to be understood alongside the larger body of evidence about what COVID-19 vaccines are designed to accomplish.
Vaccination does not provide an absolute guarantee against infection. A vaccinated person can still test positive, develop symptoms and potentially transmit SARS-CoV-2.
At the same time, WHO continues to report that COVID-19 vaccines protect against severe disease and death. This distinction between preventing infection and preventing serious outcomes is central to understanding how COVID-19 vaccination works.
Protection can also change over time, and the virus itself continues to evolve. For people at higher risk of severe disease, staying informed about current vaccination recommendations can therefore be particularly important.
Finally, people should not ignore serious symptoms simply because they have been vaccinated. Vaccination lowers risk but does not eliminate it. If someone develops significant breathing difficulties, chest pain, confusion, severe weakness or another medical emergency, they should seek urgent medical care.
COVID-19 vaccination should therefore be viewed as one important layer of protection rather than an absolute guarantee against infection.
The most reliable approach is to combine current vaccine recommendations with sensible precautions when illness or exposure occurs and to seek professional medical advice when individual circumstances require it.
