This myth about COVID vaccines keeps coming back to us, with one of the most circulated tweets of the year claiming that ivermectin is the cure. At their root, these myths claim that COVID mRNA vaccines cause cancer by altering the immune system, integrating synthetic DNA, or containing harmful contaminants that increase cancer risk over time.

These stories take advantage of people’s concerns about new medical technology, confusion about how the immune system and genetics work, and distrust of health officials. They use complicated scientific language, emotional stories, and personal experiences to seem believable, even though they don’t have strong scientific proof.

Some claims about COVID vaccines causing cancer are based on misunderstandings of vaccine components. For example, a segment of DNA, called a promoter, associated with the simian virus SV40, which was linked to early polio vaccine contamination, has been used in vaccine manufacturing to help produce the antigens found in the vaccines. Manufacturing processes ensure its removal, and no credible studies link COVID vaccines to cancer through SV40 DNA. Claims that vaccine vials contained unsafe levels of DNA come from expired, improperly stored samples, making the results unreliable. Importantly, mRNA vaccines are not gene therapy and cannot alter human DNA.

The idea that COVID vaccines cause “turbo cancer” has no scientific backing. Even the most potent carcinogens take years to cause cancer, making claims of sudden cancer spikes implausible. Epidemiological data show no increase in cancer linked to the vaccines. Reports of rising early-onset cancers started in the 1990s, long before the COVID vaccines existed.

Misinterpretations of scientific studies also fuel vaccine-related cancer claims. For example, a German study on children’s immune responses after COVID vaccination found an increase in IgG4 antibodies, which some falsely linked to cancer. However, the study did not mention cancer or immune system damage. Its findings showed that vaccinated children had mild or no symptoms when infected with COVID, indicating the vaccine’s effectiveness. These claims reflect misinformation rather than scientific reality.

Read more of our posts debunking claims about COVID vaccines and cancer.

One of the most viral rumors of the year involved the case of Alexis Lorenze. Alexis claimed that after receiving three vaccines for meningitis, pneumonia, and tetanus, she experienced a severe reaction, including swelling and pain, which she believes worsened her condition, Paroxysmal Nocturnal Hemoglobinuria (PNH).

Despite the viral tweets discussing Alexis’ dying wish, it does appear that she is still alive.

Alexis has a rare condition called Paroxysmal Nocturnal Hemoglobinuria (PNH), where her immune system attacks her red blood cells, causing them to burst. This can lead to serious issues like blood clots and liver failure. According to her TikToks and medical records, Alexis had been feeling sick for weeks before finally going to the hospital. She claims that doctors wouldn’t treat her unless she got certain vaccines. So why would doctors insist she get vaccinated in her condition?

Because PNH treatment can greatly increase the risk of serious infections, it’s standard medical practice to give vaccines for diseases like meningococcal and pneumococcal before starting treatment.

Alexis believes that a rash that appeared within 10 minutes of receiving the vaccines proves the vaccines caused her injuries. However, it’s unlikely that a vaccine could cause a reaction that quickly. A more probable explanation is the parvovirus B19 infection she tested positive for, as this virus has been known to cause similar symptoms. Additionally, her lab results show she was already experiencing blood clotting problems, which could explain the bruising she developed.

This year, anti-vaxxers claimed that vaccines are all dangerous, unnecessary, and a criminal conspiracy to make money.

Claims that COVID vaccination campaigns were only about making money are not true. Governments, healthcare organizations, and drug companies worked together to create vaccines quickly during the pandemic. The U.S. government even helped pay for vaccine development to make them available to everyone. Vaccines didn’t just save lives—they also saved money. The U.S. campaign saved an estimated $1.15 trillion by preventing over 3.2 million deaths and millions of hospital stays. The CDC and FDA also closely monitor vaccine safety through the Vaccine Adverse Event Reporting System (VAERS) and other systems. If side effects are found, they are fully investigated, and action is taken if needed.

COVID vaccines went through large clinical trials to prove they were safe and effective. Although early studies didn’t show if vaccines stopped transmission, later research showed that vaccinated people were contagious for a shorter time and infected fewer others. Vaccines reduce severe illness, hospital stays, and deaths. They are essential tools against COVID disease.

Some say diseases like measles and polio are no longer a threat, but that’s only because of vaccines. When vaccination rates drop, diseases return. For example, measles outbreaks have happened in areas with low vaccination rates. Claims that getting sick naturally is better for the immune system are also wrong. Diseases like measles can actually weaken the immune system by causing “immune amnesia,” making it harder to fight future infections. Vaccines teach the immune system how to fight germs without making people sick, providing safer, long-lasting protection.

Some anti-vaccine messages use a strategy called the “Gish Gallop,” where they flood people with so many claims that it’s hard to check them all. They might say vaccine side effects are hidden or that drug companies aren’t responsible if vaccines cause harm. This isn’t true—vaccine safety rules are very strict, and companies can be sued if they don’t follow them. Childhood vaccines protect kids from dangerous diseases like polio and measles.