26 September 2023
COVID-19Fact checkFalse

False: COVID-19 vaccines do not cause body odor

Nothing in COVID-19 vaccines change body odor. Immune response changes may affect pheromones, but the smell is not discernible unlike other common factors such as food intake.

Tweets in Chinese and Japanese, as well as a Weibo post, recently shared an image showing what looks like notices written in Japanese outside two establishments, both barring people who have been vaccinated against COVID-19 from entry.

One notice claimed people are “complaining about body odor coming from vaccinated individuals” and said the store “might ask those vaccinated not to enter the premises when crowded.”

The posts have been shared over 190 times at the time of writing. Annie Lab also found a blog post and tweets (here and here) containing the same image that were spreading in 2021 and 2022, with one of the tweets being shared over 14,000 times.

The claim about the odor, however, is false.

While we could not identify the exact location of the establishment or decide if the notice is doctored, we can be certain that COVID-19 vaccines do not cause body odor.

Clinical virologist Siddharth Sridhar from the University of Hong Kong’s Department of Microbiology said, “there is nothing in the COVID vaccine that specifically impacts body odor,” and “mRNA does not smell.”

Vaccines that were available in Japan when the image was presumably taken, which is in 2021, were developed by Pfizer-BioNTech and Moderna. Both are based on mRNA technology (Novavax became available in the country in 2022).

Sridhar said, if there are indeed changes, it would be altered pheromones when the human body was building up an immune response after being vaccinated, but such pheromones would not be discernible to the human nose, adding that factors that do affect body odor include food intake, state of health, and a person’s hormones.

Professor Ivan Hung, chief of the Division of Infectious Diseases at the HKU Department of Medicine, also told Annie Lab that there is no evidence that COVID-19 vaccines would have an impact on a person’s body odor.

Some blogs in Japan (such as this post) linked the body odor to vaccine “shedding.” The Centers for Disease Control and Prevention of the United States explains the shedding as “the release of any of the vaccine components in or outside of the body.”

A known anti-vaccine doctor, Atsushi Nakamura, also wrote in 2021 about a supposed experience of one of his patients, linking body odor to vaccine shedding. Nakamura’s clinic, according to its website, specializes in “internal medicine, psychosomatic medicine, psychiatry, and orthomolecular therapy.”

However, vaccine shedding can only happen with live attenuated vaccines, which contain a weakened form of the virus. None of the COVID-19 vaccines available in Japan is a live vaccine.

Pfizer-BioNTech and Moderna vaccines are mRNA-based. Novavax is a protein subunit vaccine. Even the ones not in use in Japan, such as Sinovac-CoronaVac and Sinopharm, are inactivated vaccines.

Johnson’s & Johnson’s’ Janssen and AstraZeneca’s vaccine are viral vector vaccines, though some countries have suspended the use of AstraZeneca vaccine in 2021 over blood-clotting concerns.

The World Health Organization explains each kind of COVID-19 vaccine here.

Similar claims about vaccine shedding have been debunked by Reuters and USA Today, among others.

False: mRNA does not alter genes

The other notice in the same image is purportedly from a medical clinic in Japan that says “vaccinated people are not treated until the safety is confirmed.”

It also says, “vaccines modify genes,” and “modified genes could be transmitted to unvaccinated patients.”

But infectious disease expert Sridhar said this 2021 allegation is also scientifically groundless.

“No, mRNA vaccines don’t alter genes and it is biologically impossible for humans to transmit genetic modifications to others (apart from their own children, of course),” he said.

The World Health Organization says on its website that the mRNA vaccines “are not live viral vaccines and do not interfere with human DNA.”

According to the National Human Genome Research Institute in the United States, the mRNA vaccine elicits an immune reaction by directing the human body to produce viral spike proteins or antigens that are recognized by immune cells.

If the inoculated person is exposed to the virus, the immune system can identify and attack the virus before it causes harm to body cells.

Similar claims have also been debunked by Reuters and Memorial Sloan Kettering Cancer Center in the United States.