Side effects from vaccination aren’t more dangerous than measles outbreaks

Myths and misinformation about measles and the measles-mumps-rubella (MMR) vaccine are persistent online, as documented in multiple reviews by Science Feedback. For decades, this misinformation has taken its toll on public health and contributed to a decline in vaccination rates that is driving a global increase in measles cases.

In early 2025, several measles outbreaks in the U.S. raised concerns among public health experts. Social media posts on Facebook and Instagram compared the extensive media coverage of what they claimed to be “15 measles cases” with the alleged lack of attention given to over two and a half million “vaccine injury reports”.

An Instagram post by chiropractor Ben Tapper garnered more than 7,000 likes. Tapper, who has over 100,000 followers on Instagram, was named one of the “Disinformation Dozen“, a list compiled by the Center for Countering Digital Hate in 2021, which identified 12 individuals responsible for nearly two-thirds of vaccine misinformation circulating online.

The implication of these posts is that the same media that ignored millions of “vaccine injury reports” is now exaggerating the risk posed by what they suggest are a few measles cases. However, the comparison made in these posts is flawed and highly misleading.

While the majority of measles cases are relatively mild, some people develop potentially serious or even fatal complications. Measles is also highly contagious. This means that once a case appears in a community, the disease has the potential to spread exponentially within it.

In contrast, a vaccine is a medical product designed to protect against a disease. While all vaccines come with some risk of side effects, this risk needs to be weighed against the benefits of vaccination. All approved vaccines have undergone rigorous clinical trials to ensure their benefits clearly outweigh any known or potential risks.

Moreover, what the posts called “vaccine injuries” are in reality adverse events—medical events that happen after vaccination but aren’t necessarily caused by the vaccine. Therefore, the claim that vaccination has caused millions of “vaccine injuries” is also inaccurate. We explain in more detail below.

Why are measles cases a public health risk?

Measles is an infectious disease caused by the measles virus, which infects only humans. The disease typically starts with cold-like symptoms resulting from infection of the respiratory tract. As the infection spreads throughout the body, the symptoms evolve into high fever and the characteristic rash.

Most people recover from measles in about a week without lasting effects. This relatively mild nature of many cases has led some to consider measles as not being dangerous. But this isn’t true.

Roughly three in ten people infected with measles will develop complications, including ear infections that may lead to deafness, pneumonia (lung infection), and encephalitis (brain inflammation). Even years after recovering from measles, some individuals may develop a very rare neurological disease called subacute sclerosing panencephalitis, which has no cure and is almost always fatal.

About 20% of the people who get measles require hospitalization, and roughly 1 in every 1,000 dies. This is often not due to the disease itself but because the measles virus weakens the body’s ability to fight off other infections, even those it encountered before, an effect called “immune amnesia“.

Children under five are particularly vulnerable to developing complications from measles. Pregnant people also have an increased risk of complications both for the mother and the fetus^[1].

The other reason why measles is concerning is because it is one of the world’s most contagious diseases. The disease spreads by touching a contaminated surface or by breathing droplets from coughs or sneezes from an infected person. According to Johns Hopkins Medicine, “[n]ine out of 10 unimmunized children who are in contact with an infected person will contract the virus”.

The measles vaccine is highly effective but preventing outbreaks requires that enough people get vaccinated

Fortunately, measles is a vaccine-preventable disease. The measles vaccine was introduced in the U.S. immunization schedule in the 1960s and replaced with the combined vaccine against measles, mumps, and rubella in the 1970s. The measles-mumps-rubella (MMR) vaccine contains a live, weakened (attenuated) virus that stimulates immunity but can’t cause disease in people with a normal immune function.

A single dose of the MMR vaccine is over 93% effective at preventing measles infection. Two doses provide up to 99% protection, generally for a lifetime.

Widespread vaccination has played a significant role in eliminating measles from many countries. In the U.S., the disease was declared eliminated in 2000. This doesn’t mean there have been no cases of measles since then, but rather that the virus is no longer spreading within the population. New cases generally arise from people who contracted the disease abroad and then returned to the U.S.

But because measles is so contagious, at least 95% of the population needs to be vaccinated to effectively prevent the spread of the disease.

It is also important to keep in mind that not everybody can get the vaccine, and that the vaccine isn’t 100% effective. About 1% to 3% vaccinated individuals will not develop an adequate level of protection and will still be susceptible to infection if exposed to the virus. Infants younger than one are also unprotected as they haven’t yet received their measles vaccination. In addition, because the measles vaccine is a live attenuated vaccine, it isn’t recommended for people with a weakened immune system, who may develop the disease even from a weakened virus^[1-4].

Therefore, a small percentage of the population can’t receive the vaccine and has to rely on herd immunity for protection. However, if many people who can safely receive the vaccine choose not to vaccinate, there is a high risk that the coverage falls below the optimal level of 95%, making outbreaks more likely.

This is what happened recently with the U.S. outbreak in Texas. What started in late January 2025 as two measles cases associated with international travel in unvaccinated individuals in Gaines County, Texas, expanded into 124 cases and a child’s death in less than a month.

This is the largest outbreak in the U.S. in nearly 30 years, and it isn’t by chance that Gaines County was at the epicenter. This region has one of the highest rates of vaccine exemption in Texas at nearly 18% during the 2023-2024 school year as compared to the statewide average of 4%.

Undervaccinated communities like this are the perfect breeding ground for measles to spread. And these incidents serve as a stark reminder of the severe consequences that “a few” measles cases can have within a community.

Adverse events aren’t “vaccine injuries”; vaccines undergo thorough testing to ensure that their benefits outweigh any potential risks

The posts mentioned “2,659,050 vaccine injury reports”, citing the U.S. Centers for Disease Control and Prevention (CDC) as their source. Some posts, like this one on Instagram, were more specific and referenced Openvaers.com.

OpenVAERS is a website that mirrors and extracts data from the U.S. Vaccine Adverse Event Reporting System (VAERS). According to research by Logically—a tech company specialized in analyzing and fighting disinformation—shared with Vice Media, the site was created by web designer Liz Willner in 2021 and has been used to spread vaccine misinformation by misrepresenting VAERS reports as causally linked to vaccination.

VAERS records adverse events that occur after vaccination. However, the number of reports alone doesn’t demonstrate that the vaccine caused the adverse events.

In any population, there is a baseline rate of medical events, illnesses, and deaths that occur regardless of vaccination status. As a result, many adverse event reports might simply reflect incidental health problems unrelated to vaccination. Unusually high numbers of certain adverse events can help authorities identify potential safety problems with a vaccine. This was how researchers identified a rare, but serious, side effect associated with a rotavirus vaccine.

However, VAERS reports alone aren’t enough to establish a causal relationship; the cases need to be investigated in detail and compared to the baseline rate of the adverse event in that specific population to determine whether the vaccine was indeed the cause.

As the VAERS official website explains, a high number of adverse event reports doesn’t necessarily indicate a safety problem with a vaccine. Higher reporting can result from other factors, such as increased public awareness or changes in reporting requirements. A clear example of this is seen with COVID-19 vaccines.

In the case of COVID-19 vaccines, healthcare providers were required by law to report all serious adverse events that occurred following vaccination—including hospitalization and death—“regardless of causality”. In contrast, for other vaccines like the flu vaccine, healthcare providers only have to report certain adverse events.

In light of the above, the claim that vaccines have caused more than two and a half million “vaccine injuries” lacks scientific support because VAERS reports cannot be regarded as stand-alone proof of causality as the social media posts imply. This represents a misuse of the database, which the official VAERS website warns against before granting access to any data.

Conclusion

Viral posts comparing the media coverage of measles cases and alleged “vaccine injury reports” greatly exaggerate the risks associated with vaccination. At the same time, they downplay the threat posed by an infectious disease as contagious as measles, which can rapidly spread in communities with low vaccination rates and lead to serious complications.

The alleged “vaccine injuries” mentioned in these posts are in reality reports of adverse events. These are medical events that happened after vaccination but weren’t necessarily caused by the vaccine. All approved vaccines undergo rigorous testing to ensure they are effective at preventing the disease and their benefits outweigh the potential risk of side effects.

REFERENCES

• 1 – Khalil et al. (2024) Pregnant women and measles: we need to be vigilant during outbreaks. eClinical Medicine.
• 2 – Monafo et al. (1994) Disseminated measles infection after vaccination in a child with a congenital immunodeficiency. Journal of Pediatrics.
• 3 – Angel et al. (1998) Vaccine-associated measles pneumonitis in an adult with AIDS. Annals of Internal Medicine.
• 4 – Bitnun et al. (1999) Measles inclusion-body encephalitis caused by the vaccine strain of measles virus. Clinical Infectious Diseases.