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A New Study Confirms Anti-Vaxxers Are Fueling The Rise Of Measles And Whooping Cough

"These unvaccinated individuals are like the tinder that starts a roaring fire."

A new NIH-funded study confirmed the association between vaccine refusals and recent U.S. outbreaks of measles and pertussis.

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According to the study, "unvaccinated individuals comprised substantial proportions of cases in measles and some pertussis [whooping cough] outbreaks, and vaccine refusal — as measured by population-level vaccine exemption rates — was associated with an elevated risk for measles and pertussis, including among fully vaccinated individuals."

The most common form of vaccine refusal is when parents claim non-medical exemption to a school's mandatory immunization requirements, says Saad Omer, Ph.D., M.P.H, professor of global health at Emory University and senior author of the study. Non-medical exemptions are given when parents claim the vaccines conflict with their religious beliefs or go against their personal or philosophical morals, and there has been a steady increase of them in the last 20 years.

"These non-medically exempt children make up 2/3 of those who are eligible for vaccines, which includes people who can't get vaccinated for medical reasons," Omer says.

Measles was declared eliminated in the U.S. in 2000, but in 2014 there were a record 668 cases.

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The study found that out of the 1,416 measles cases reported in the U.S. between 2000 and 2015, more than half (56.8%) were in unvaccinated individuals. And among those (for whom detailed medical records and the reasons for non-vaccination were available) 70% had a non-medical exemption from parents. More importantly, most of these unvaccinated cases make up the very dangerous "first wave" of the epidemic, Omer says, which is what triggers a mass spread.

Measles is a highly contagious disease spread through coughing and sneezing, which can cause a high fever, cough, red and watery eyes, mouth sores, and a rash. It usually goes away within three weeks, but in vulnerable patients it can cause pneumonia, brain swelling, and even death. The vaccine is 97% effective at preventing measles, so in rare cases vaccinated people can still be infected. "This is why vaccine refusal is so risky, because no vaccine is 100% effective even if everyone does the right thing and gets it," Omer says.

Pertussis (whooping cough) hit a national low in 1977, but since 2005 there have been over 45,000 cases.

CDC Public Health Image Library / Wikicommons / Flickr user Sanofi Pasteur CC / Via / Flickr: sanofi-pasteur

The study found that in eight nationwide pertussis outbreaks, between 59-93% of the cases were individuals who were intentionally unvaccinated or under-vaccinated (fewer than the recommended pertussis vaccine doses). Pertussis outbreaks have also happened among highly vaccinated populations, says Omer, which is evidence of a decreasing or "waning immunity" — and the only thing to combat that would be increased immunization rates.

Pertussis is a highly contagious respiratory tract infection that causes a severe, painful cough that can last for up to 10 weeks or longer. It affects all ages, but it can be especially serious and life-threatening in young children and babies. There is a multi-dose vaccine (Tdap) to prevent pertussis among unvaccinated and vaccinated individuals, who can still get a less severe form of the disease.

When too many people go unvaccinated, it can affect an entire population's "herd immunity."

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Vaccination is intended to not only keep the individual safe and healthy, but the entire community population. When most of a community is immunized against an infectious disease, something called "herd immunity" happens, which means the chance of an outbreak is very low and it can be easily contained.

"Non-medically exempt unvaccinated people provide pockets of susceptibility which spread to everyone — they are the tinder that starts a fire, even among damp wood," Omer says.

Herd immunity protects people who are immunosuppressed or can't get vaccinated, such as cancer patients.

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Some people are not eligible for vaccines. This includes young infants, pregnant women, and immunocompromised individuals such as patients with HIV/AIDs, cancer, or recent organ transplants.

Herd immunity is especially important for these people because they are both at higher risk of severe or potentially fatal consequences if infected and they depend on herd immunity alone for protection.

The study points out a need for more strategic policy to increase vaccine uptake among children.

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The study states that in order for any legislation which overrides parental decisions to work, there needs to be a clear demonstration of the magnitude of risks and harms of vaccine refusal. This study aims to reinforce those risks and provide evidence for stricter vaccination laws. "People must know that it is in everyone's best interest to have higher vaccination rates and eliminate pockets of susceptibility," Omer says.

This can be done through stricter laws, vaccine mandates, or making it more difficult to obtain a non-medical exemption (which may require patient education and consulting with a doctor). "It shouldn't be as simple as printing a form — it should be significantly easier to vaccinate your child than it is to claim exemption," Omer says.

NIH Director Francis Collins says the study is "an important reminder" of effective communication about vaccines.

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"Some parents continue to express concern about a possible link between vaccines and autism spectrum disorders, but the original report claiming this connection has been debunked and retracted," Collins says in a recent commentary of this new study. "A large number of carefully designed follow up studies have been carried out, and the overwhelming weight of scientific evidence shows no evidence for such a link."

Collins cites the study as an important way to send the message to parents that they should get their children vaccinated. The successful eradication of potentially fatal infectious diseases depends on it.