Are ongoing concerns about vaccine safety to blame for the measles epidemic?

Date: Feb-05-2015 In 2000, measles was declared eliminated in the US. But last year saw a record number of measles cases since - 644 over 27 US states. This year is unlikely to be any better, with 102 cases reported so far. In this spotlight, we look at whether ongoing concerns surrounding vaccination safety are behind the measles epidemic.

According to the CDC, the MMR vaccine is 93-97% effective at preventing measles.

Measles is a highly contagious respiratory disease caused by infection with the morbillivirus. Onset of the disease usually begins with a fever, cough, inflamed eyes, runny nose and sore throat, before a red, blotchy rash appears all over the body.

Common complications of the virus include ear infections and diarrhea, while more severe complications include pneumonia - the most common cause of measles-related death in children, and swelling of the brain, known as encephalitis, which can cause convulsions, deafness and brain damage.

Measles first became a "nationally notifiable" disease - a condition in which health care providers had to report all diagnosed cases - in the US in 1912. Over the following decade, there were around 6,000 measles-related deaths in the country each year.

In the 1950s, around 3-4 million people in the US became infected with measles annually, with around 48,000 hospitalizations and 400-500 deaths from the virus each year. Almost all children contracted measles by the age of 15, and around 4,000 people developed measles-related encephalitis each year.

The rise of the measles vaccine

But in the early 1960s came the first licensed measles vaccine in the US, created by American biomedical scientist John F. Enders and colleagues. In 1968, an improved measles vaccine - created by American microbiologist Maurice Hilleman and colleagues - was distributed in the US, and this vaccine has been used ever since.

The vaccine - which in 1971, was administered in combination with mumps and rubella to form the MMR vaccine, or with mumps, rubella and varicella to form the MMRV vaccine - dramatically reduced the the number of measles cases in the US.

It was first administered in a single dose, which by 1981, had reduced the number of reported measles cases by 80%, compared with the previous year. But in 1989-91 came a severe measles outbreak, which saw 55,622 Americans become infected with the virus and 123 associated deaths. The outbreak was attributed to low vaccination rates; 90% of all fatalities occurred in people who were not vaccinated.

As a result, a number of health bodies - including the Advisory Committee on Immunization Practices (ACIP) and the American Academy of Pediatrics (AAP) - recommended that the MMR vaccine be given to all children in two doses instead of one. This led to the Vaccines for Children (VFC) program being introduced in 1994.

Now, current recommendations from the Centers for Disease Control and Prevention (CDC) state that all children should receive two doses of the MMR vaccine, with the first dose to be administered at the age of 12-15 months and the second dose to be given at the age of 4-6 years.

For adults who are not immune to the measles virus, the CDC recommend that they should receive at least one dose of the MMR vaccine.

Compared with the pre-vaccine era, the CDC say the MMR vaccine has led to a 99% reduction in measles cases in the US, and in 2000, measles was declared eliminated in the country - meaning there had been no continuous disease transmission for over 12 months.

Recent outbreaks have led to concern

There will always be some cases of measles in the US, as it can still be brought into the country by individuals from other countries who have not been vaccinated. But between 2000 and 2007, the number of measles cases reached a record low, with only 37 cases being reported in 2004.

In recent years, however, the number of measles cases in the US has risen. In 2008, the number of annually reported cases passed the 100 mark for the first time since 2001, and in 2011, more than 200 cases were reported.

But last year saw the highest number of reported measles cases in the US since the virus had been declared eliminated. There were 23 measles outbreaks in 2014, causing 644 people to become infected.

According to the CDC, the majority of these cases were brought into the country by travelers from the Philippines - where a large outbreak of the virus was occurring at the time - and most of the people who became infected in the US were part of unvaccinated Amish communities in Ohio.

But while last year's statistics seem bad, this year's are set to be even worse. Last month alone saw 102 measles cases reported over 14 US states, including California, Texas and Washington. The majority of these cases are thought to have stemmed from Disneyland, CA, where a number of people reported developing the virus after visiting the amusement part in mid-December.

In a press briefing at the end of last month, Dr. Anne Schuchat, director of the National Center for Immunization and Respiratory Disease at the CDC, said this year's outbreak is a concern:

"It's only January and we have already had a very large number of measles cases - as many cases as we have all year in typical years. This worries me and I want to do everything possible to prevent measles from getting a foothold in the United States and becoming endemic again."

And according to the CDC, vaccination is the key to getting a "foothold" on measles in the US, and it is primarily lack of vaccination that has contributed to the recent outbreaks.

Safety of MMR vaccine is still questioned

While measles vaccination coverage across the US looks positive overall - with the CDC reporting a 91.9% MMR vaccine coverage among children aged 19-35 months in 2013 - it varies significantly by state.

For example, Colorado - which has been affected by the latest measles outbreak - only has an MMR vaccine coverage of 82%, and a 2013 report from the CDC revealed that 17 US states have an MMR vaccine coverage below 90%.

A report from the CDC found that last year, 79% of measles cases occurred among people who opted out of the MMR vaccine due to personal beliefs.

The CDC say the MMR vaccine is safe, and one dose of the vaccine is around 93% effective at preventing measles, while two doses is approximately 97% effective. So why are many people still not getting themselves or their children vaccinated?

Primarily, it is down to religious or personal beliefs. A report from the CDC found that last year, 79% of measles cases occurred among people who opted out of the MMR vaccine due to personal beliefs. And these personal beliefs tend to be associated with worries that the vaccine is unsafe for children.

This belief stems from a study published in The Lancet in 1998, conducted by British researcher Andrew Wakefield and colleagues from the UK. In this study involving 12 children, Wakefield and his team suggested a link between the MMR vaccine and autism.

Though other studies were unable to reproduce the findings, Wakefield's research had a significant impact on vaccination coverage. In the UK, MMR vaccination rates fell from 90% to 80%, while measles cases began to rise.

The study has since been retracted by The Lancet, having been deemed as "fraudulent" after undisclosed financial conflicts of interest were revealed by a journalist called Brian Deer in 2011. As a result, Wakefield lost his medical license. But regardless of this outcome, he stands by his findings, and so do many others.

One of the most well-known supporters of Wakefield's claim is former Playboy centerfold Jenny McCarthy, whose son developed autism, which she attributes to vaccination. She claims that current vaccines are unsafe and contribute to autism and other disorders.

"I do believe sadly it's going to take some diseases coming back to realize that we need to change and develop vaccines that are safe," she said in an interview with the Chicago Sun Times last year. "If the vaccine companies are not listening to us, it's their [...] fault that the diseases are coming back. If you give us a safe vaccine, we'll use it."

Many parents in the US support McCarthy's statement, but the CDC and other health organizations warn that this perception toward vaccination is putting the public's health at risk.

MMR vaccine: 'safe, effective and highly recommended'

Writing in an article for Forbes, Steven Salzberg, a professor of biomedical engineering, computer science and biostatistics at Johns Hopkins University School of Medicine in Baltimore, MD, says this latest measles epidemic has been "fueled by growing enclaves of unvaccinated people."

"Anti-vaxxers have been relentless in the efforts to spread misinformation," he adds. "Despite overwhelming scientific evidence that vaccines are beneficial, they endlessly repeat a variety false claims, such as vaccines cause autism."

"Over the past 15 years, dozens of studies involving hundreds of thousands of people have shown convincingly that neither vaccines nor any of the ingredients in them are linked to autism," he continues. "Vaccines are not only safe, but they are perhaps the greatest public health success in the history of civilization."

Both Prof. Salzburg and Dr. Schuchat note that we should not underestimate how serious measles can be. Around 1 in 10 children with measles develop ear infections, which can lead to hearing loss, and around 1 in 20 develop pneumonia. In this outbreak alone, a quarter of infected individuals have been hospitalized as a result.

"The news this year is concerning and serves as a warning that measles is still coming into the United States and that unvaccinated people can get exposed," said Dr. Schuchat in a press briefing.

"These outbreaks the past couple of years have been much harder to control when the virus reaches communities where numbers of people have not been vaccinated and, of course, when the virus comes into the country and exposing people at large venues where many people gather, the chances of exposure are greater," she added.

As such, the CDC and health care professionals across the country are calling for all individuals to ensure they receive the measles vaccination. Dr. Schuchat said:

"I want to make sure that parents who think that measles is gone and haven't made sure that they or their children are vaccinated are aware that measles is still around and it can be serious. And that MMR vaccine is safe and effective and highly recommended."

Whether Dr. Schuchat's reassurance that the MMR vaccine is safe will encourage increased vaccination coverage going forward is unclear. But Prof. Salzburg says it is possible the measles epidemic itself will change people's views about vaccination.

"Perhaps the Disneyland epidemic will finally convince parents, schools, and state legislatures that they need to insist that children get vaccinated before going to school," he wrote in Forbes. "Perhaps it will also convince parents to stop listening to nonsense, and choose wisely by getting their children vaccinated against measles. We won this battle before, and we can win it again."

Written by Honor Whiteman

Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.