Vaccines, get your vaccines
Many Americans are travelling abroad without important vaccines, leaving themselves open to various dangerous health risks, according to a pair of new studies
One of the studies focused on measles, while the other focused on cases of acute hepatitis A. Both took in American travellers heading overseas, and both found that despite the wealth of information available on the subject, many Americans are failing to effectively vaccinate themselves against these easily preventable infections. However, Dr Emily Hyle of the division of infectious diseases at Massachusetts General Hospital in Boston, US, said that increased education about the dangers of measles – such as letting people know that it has an infection rate of 90 per cent per single exposure for those who have not been vaccinated – and the importance of vaccinations remain key to increasing uptake.
“When we think about an exposure,” she said, “it doesn’t have to be by contact. If someone who has measles walks through a room, infection remains in that room for up to two hours.” Hyde and her colleagues at the hospital analysed data from 40,810 US adults who took part in pre-travel consultations between 2009 and 2014 at 24 different sites, each of which was part of the national Global TravEpiNet network, a series of clinics supported by the Centers for Disease Control and Prevention (CDC). Sixteen per cent of those analysed were eligible for vaccination (i.e. they had not been immunised or were under-immunised), but fewer than half of these received the MMR (measles, mumps and rubella) vaccine before heading off on their travels.
Dr Daniel Morgan, a hospital epidemiologist with the VA Maryland Healthcare System, said that the study ‘identifies an important failure to vaccinate susceptible patients travelling abroad’. “Measles can be a deadly disease that is completely preventable through vaccination,” he said. “And measles in the US is largely related to foreign travel without vaccination.”
“Measles is one of the most contagious diseases in the world,” added Dr Hyle, “and even brief exposure can lead to infection. Many travellers heading to developed countries, including those in Europe, might not realise that there are outbreaks of measles occurring in those areas, and they are at risk [of] becoming ill.”
The second study, which reported on 30 cases of acute hepatitis A observed in US travellers who had spent time in Tulum, Mexico, between 6 January and 20 March this year, found that of the infected persons, 26 had not received a vaccination for hepatitis A before travelling; 79 per cent of patients had eaten seafood during their trips, and 62 per cent had specifically eaten raw seafood. “The recommendation is not to consume undercooked meats or seafood while travelling to a hepatitis A-endemic area,” said Dr Monique Foster of the CDC. “Hepatitis A has a very, very high attack rate. About 70 per cent of people exposed will become ill, so that’s why we also recommend post-exposure prophylaxis of any household contacts of ill individuals.” Scott Weisenberg, MD, an infectious disease physician with California’s Alta Bates Summit Medical Center, meanwhile, said that the vaccination for hepatitis A ‘is part of any standard pre-travel health assessment and is highly effective. It is recommended for most areas of the world.”
A cause for concern
Considering the issue of measles more broadly, travel health experts have said that the disease remains a severe – and unnecessary – risk for many travellers, regardless of their destination, and that vaccination remains the best method of preventing it. Data taken from 57 travel and tropical medicine clinics across six continents has shown that, between 2000 and 2014, these clinics saw 94 reported cases of measles – worryingly, two thirds of these occurred after 2010, suggesting that the problem is getting worse rather than better. Those affected included tourists, business travellers, and people visiting family and friends.
“We think measles is definitely something people should be concerned about,” said the CDC’s Mark J Sotir, “[and] specifically getting vaccinated against.” The CDC recommends that all children receive two doses of measles vaccine by the age of six – this should provide 97-per-cent effectiveness against measles infection – and that children and adults engaging in international travel should definitely have these vaccinations. “We feel that people should probably be evaluated by a healthcare provider four to six weeks before they [travel],” said Sotir.
Declining rates of vaccination, added the CDC’s Dr Douglas H Esposito, are a ‘broad public health issue’. “We recommend that people be up to date on routine vaccinations as well as destination-specific vaccinations,” he said.