28 things your doctor wishes you knew about vaccines

With Covid-19 vaccines being rolled out around the globe at warp speed, vaccines are now facing even greater scrutiny than ever before – and a lot of mistrust. Instead of listening to unqualified opinion online, find out what doctors wish you knew about them.

Increased medical care, better nutrition, and cleaner and less crowded living conditions have certainly had an impact on the spread and treatment of infectious diseases over the years. But the World Health Organization (WHO) reports that vaccines have played an even more important role in the drastic reduction of disease. If there’s no vaccine for a disease (as has been the case with Covid-19), then all we have is hygiene, says Dr Kathryn M. Edwards, a spokesperson for the Infectious Diseases Society of America (IDSA). And for some highly contagious diseases like measles, hygiene may not be enough. While Covid-19 may infect three to four people, measles can infect 15 to 20. That said, you still need to focus on hygiene.

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As an example of this, the WHO points to Haemophilus influenzae type b (Hib), a type of bacteria that can cause brain and blood infections, including meningitis. Due to the vaccine, the disease is now mostly a footnote. Numerous other viruses that most of us are thankfully unaware of could come back with potentially deadly results if we stopped vaccinating, the agency says. (By the way, Hib is not related to the influenza virus.)

“No vaccine is 100 percent effective,” says Dr Edwards, although some (like measles) come very close. In a major outbreak, says WHO, immunised people can become infected, though not at the same rate as people who have not been immunised.

The other issue is that up to 5 percent of people may not respond to a vaccine, according to the CDC. That’s why some vaccinations require additional boosters. It’s also possible that the vaccine and the infection crossed paths so to speak. In other words, some people are infected just before or after receiving the vaccine and develop symptoms because the immune response hasn’t had time to kick in. (It can take the body a couple of weeks to react to the vaccine and create protective antibodies.)

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Even though vaccines contain bits and pieces of the same bacteria or viruses that cause disease, the vaccine itself is not going to make you sick from the disease. That’s because vaccines are usually made from inactivated (killed) organisms or “live attenuated,” meaning the germ is greatly weakened. Live attenuated vaccines give you really robust protection but they can be dangerous to some people, such as those with compromised immune systems. Inactivated vaccines don’t give you as much protection, meaning you may need more than one dose. They are, however, safer for more people. There are two other vaccine types as well. Subunit, recombinant, polysaccharide, and conjugate vaccines use particles of an organism while toxoid vaccines use a toxic substance produced by the germ – not a version of the germ itself.

One of the leading arguments of the anti-vaccination movement is that vaccines – particularly the measles vaccine – cause autism in children. “This has been totally discredited,” says Dr Schaffner. According to the CDC, there is no link between vaccines and autism; their experts point to nine separate CDC-funded or conducted studies since 2003 that have disproven the supposed connection between the preservative called thimerosal – found in trace amounts in some vaccines – and autism. The vaccines for measles, mump, and rubella have all been cleared of any connection to the condition.

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The CDC reports that when people get a second shot (or a booster) of a vaccine, the protection may reach nearly 100 percent effectiveness. Some vaccines require a third shot. In adults, the Td (tetanus, diphtheria) vaccine requires a booster every 10 years. Other adult vaccines that require extra doses are hepatitis A (two doses given six to 18 months apart), hepatitis B (three doses over six months), and human papillomavirus (also three doses over six months). The recommended vaccination schedule for children is complicated and several vaccines require multiple doses including DTaP (diphtheria, tetanus, and pertussis), polio, MMR (measles, mumps, rubella) and chickenpox. Of course, the flu vaccine needs to be repeated annually.

Vaccine-preventable diseases like measles, mumps and even HPV can be fatal, but the vaccines that prevent the disease are not. The CDC notes that only some vaccines contain trace amounts of preservatives and other ingredients like formaldehyde, mercury and aluminium – and in those cases, the levels are not nearly enough to be harmful. They also report that the human body is exposed to higher levels of these chemicals from the environment than you would get from vaccines. Some vaccines may give you a minor illness. “The only vaccines that would be capable of giving the disease are live vaccines, an example is the measles vaccine,” says Dr Edwards. “Some people seven to 10 days after the vaccine get a fever and rash. That’s weakened measles.” Healthy people shouldn’t have any problem with this, although immunocompromised people need to talk to their healthcare provider.

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Some vaccines do use a preservative called thimerosal, which contains ethylmercury, but there’s been no evidence showing it can cause harm in the low doses you’d find in an immunisation. The compound is used as a preservative in multi-dose vaccines to prevent them from getting contaminated, says Dr Edwards. The name can be easily confused with methylmercury, which is not found in vaccines. Methylmercury can damage the central nervous system – but again, it’s not found in vaccines. It is, however, found in fish from air pollution that settles in water. The body gets rid of ethylmercury way faster than methylmercury, making it less likely to do damage. Even so, ethylmercury was taken out of childhood vaccines in 2001 to ease any concerns.

Vaccinations contribute to a healthier community. People with weakened immune systems – and those for whom a vaccine may not be as effective or even recommended – can be in danger if they run into someone who is sick. When everyone keeps up with vaccinations, we prevent outbreaks that could have numerous fatalities. “We know that if we have a population that is vaccinated, then it reduces the ability of the virus to spread,” says Dr Edwards. “If everyone around us vaccinated, we can really cut down remarkably the spread of the infection.” That’s called herd immunity. Experts are hoping this will be one benefit of the Covid-19 vaccine.

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