Anti-vaxxers are seizing on an interview Sean Hannity conducted with HHS Secretary Robert Kennedy Jr. to say that bird flu vaccines may not work well and could make the virus stronger, cause more chickens to get sick, and increase egg prices.

These claims show a basic misunderstanding about vaccines and viruses. The idea of a “leaky vaccine” does exist. But as proof, they point to Marek’s disease in chickens. In that case, the virus changed, causing a stronger version that could make unvaccinated chickens sicker. But this has only happened with Marek’s disease, not with other diseases. Even with this “leaky vaccine,” vaccination greatly reduced how much the disease spread and how many chickens got sick. Because of vaccines, chicken deaths from Marek’s disease dropped by 99% from 1970 to 2006.

Another incorrect claim is that vaccines turn birds into mutation factories. Viruses naturally change or mutate over time. But most mutations happen when a lot of sick animals spread the virus. Vaccines actually slow down virus spread, making it harder—not easier—for new mutations to form.

He also claims that chickens would gain natural immunity if they were allowed to catch bird flu. The problem with this idea is that flu viruses mutate very quickly. Also, immunity against one type of flu virus doesn’t always protect against other types.

Scientists around the world agree that vaccinating poultry safely prevents bird flu outbreaks. It also protects farms and reduces the chance that bird flu might spread from birds to people. Vaccines are a safe and effective way to control disease, protect animals, and keep food supplies stable.

The old myth about measles outbreaks is once again endemic, with anti-vaxxers claiming that the measles vaccine itself transmits the virus through “vaccine shedding,” spreading infection to vulnerable individuals.

This tweet falsely says that the measles vaccine spreads measles through something called shedding. It’s true that the MMR vaccine (which protects against measles, mumps, and rubella) has live viruses in it—but these viruses are weakened, so they can’t make people with healthy immune systems sick.

The MMR vaccine has live viruses in it, but they are special versions that are different from the real ones that cause disease. Scientists can tell them apart by looking at their genotype, kind of like how you can recognize someone by their fingerprint.

When someone has a real infection, their body can release viruses through a process called shedding. If someone else catches the virus and gets sick, that’s called transmission. Since the vaccine uses a virus, a tiny bit of shedding might happen after you get the shot. But that doesn’t mean it spreads disease.

Here’s what’s important to know: shedding is not the same as spreading illness. The virus in the vaccine is so weak (attenuated) that it can’t cause measles. Even though the vaccine inserts mention shedding, it’s just a possible risk, not something that’s ever actually happened. In fact, there’s never been a real case of anyone getting measles from someone who got the vaccine.

In fact, the Infectious Disease Society of America (IDSA) recommends people living with immunocompromised still receive the MMR vaccine.

A new video from Children’s Health Defense claims that COVID vaccines were designed to spread vaccine materials (such as spike proteins) from vaccinated to unvaccinated people, causing health problems in both groups.

Shedding happens when a person who got a vaccine with a live virus releases that virus from their body, which might then be passed to someone else.

But the mRNA COVID vaccines don’t use live viruses. Instead, they use mRNA, which is like a set of instructions. It tells your cells to make spike proteins. These proteins show up on the outside of your cells so your immune system can recognize and fight the virus in the future.

The video claims that unvaccinated people can be exposed to spike proteins or mRNA just by being around someone who got the vaccine. But the video gives no evidence of this and doesn’t explain how it would even happen. The mRNA doesn’t make more copies of itself in your. cells—it’s just used once as instructions. Then breaks down, usually within a day. The mRNA is so unstable that the vaccine has to be stored at very cold temperatures, sometimes as cold as -70°C.

The video also says that this shedding is part of a plan to hurt people on purpose. Such a conspiracy would be almost impossible because creating and delivering vaccines involves thousands of scientists, researchers, companies, and governments worldwide. It would be nearly impossible for so many people, across many countries and languages, to secretly plan and keep hidden something harmful without anyone uncovering strong proof. Mathematically, the more people involved in a conspiracy, the harder it becomes to hide it over time.