After polio, eradicating measles with help of new drug may come next
Measles tops the list of diseases that can be stamped out from the world forever. But since measles is highly infectious, 95% of all children in all populations need to be given two doses of the vaccine.columns Updated: Apr 20, 2014 02:23 IST
Good news on the measles front. A new anti-viral drug may prevent measles in people who are not vaccinated but have been exposed to infection. Like the flu, measles is very contagious and turns ill people into efficient infection machines that sicken everyone within talking distance.
Animal tests showed that three days after infection, the new drug -- with the very forgettable name of ERDRP-0519 -- was able to suppress a lethal “measles-like” canine distemper virus in ferrets. Viruses are not alive, so anti-viral drugs do not aim to kill, just to stop replication. ERDRP-0519 does this by blocking measles’ RNA polymerase, an enzyme vital for replication. All the animals treated with the drug not only lived but also developed a “robust” immunity against the virus, US scientists reported in Science Translational Medicine.
Measles tops the list of diseases that can be stamped out from the world forever, like small-pox and, hopefully soon, polio. But since measles is highly infectious -- a sick person can infect nine out of 10 people without immunity -- 95% of all children in all populations need to be given two doses of the vaccine. Roughly 15% of vaccinated children do not develop immunity from the first dose, thus, outbreaks can happen even if only 80% are fully immunised.
Measles usually causes symptoms of high fever, running nose and that appear 10 days after infection, followed by a rash that appears over the face and rapidly extends down to cover the whole body over the next three days. Malnourished children — 46% children in India are underweight and 38% stunted, with weakened immunity to begin with — are at risk of ear infections, pneu--monia and encephalitis (infection of the brain membrane that causes convulsions, seizures, retardation and death), and death.
Of the 2 crore children worldwide who did not get vaccinated even once in 2010, a third (67 lakh) lived in India, shows World Health Organisation (WHO) data. In November 2010, India launched a massive polio-style measles vaccination project in 14 high-burden states, in a three-phase campaign that got over last year. It targets to reduce infections and deaths by 90% by 2014. It’s effectiveness will show up in data released next year.
The WHO recommends all children get two doses -- the first when they are 9 months old and the second dose between 12 and 15 months - of MMR vaccine that protects against measles, mumps and rubella (German measles). Less than one in hundred who get both shots get the infection, and even if they do-a rare situation known as “vaccine failure”-they are not contagious and do no spread infection.
Children missing vaccination the reason why measles continues to kill 1.58 lakh children each year, mostly in poor countries. Almost all are under the age of 5, which means 430 children die of measles-related complications each day.
To work in humans, ERDRP-0519 will have to be given after someone has been exposed, but before the onset of symptoms. This can take two weeks, so it gives public health workers time to treat all the social contacts of someone who has developed measles.
The only potential risk of the drug is that it may lead to the development of mutant drug-resistant trains of measles viruses, much like antibiotic-resistant bacteria. And if mutant virus turns more infectious and deadly than the natural one, the existing vaccine may become ineffective against it.
The US team tested the drug against measles virus in culture and found it did form resistant mutants, but they were all less transmissible and deadly than natural measles. But then, flu mutants resistant to the anti-viral drug Tamiflu seemed equally unthreatening in similar lab tests until 2007, when a new resistant mutant took over and went viral.
A drug is needed more now than ever before, more so with public health officials in New York City confirming earlier this month, a fully-vaccinated woman caused an outback in the US, infecting four people. Patient zero was a vaccinated 22-year-old theatre employee who, speculate health officials, remained infectious because of the complete absence of the virus in the environment, which serves as a natural booster dose. But with vaccination making infection rarer in developed countries and the world, such outbreaks are likely to increase.
Measles eradication globally has to be driven by vaccination, with the new drug being used exclusively to rapidly suppress local outbreaks among people with vaccination coverage. With the drug can act in synergy with the vaccine to plug gaps in vaccination coverage, stamping out measles may just be easier than polio.