There are growing fears over the safety of a dengue vaccine that was approved for sale in Mexico two years ago as a result of new evidence that it could increase the risk of contracting a severe form of the disease.
The former head of the Federal Commission for Protection Against Health Risks (Cofepris) authorized the drug developed by French pharmaceutical company Sanofi on December 9, 2015, reportedly ignoring warnings about its potential danger from the National Institute of Public Health (INSP).
The decision approved by Mikel Arriola — now seeking election to become the next mayor of Mexico City for the Institutional Revolutionary Party (PRI) — made Mexico the first country in the world to approve the groundbreaking vaccine.
Several other countries, including the Philippines, Brazil, Guatemala, Thailand and Singapore, followed.
But the Philippines — where a massive immunization program was also launched — has now suspended the use of the vaccine called Dengvaxia after new evidence, confirmed by the drug maker, was revealed showing that at least 997 children had “adverse events following immunization.”
The vaccine may provoke a more severe reaction among people who have never previously contracted dengue, Sanofi said following its own subsequent analysis.
Consequently, the vaccine shouldn’t be recommended for such people, the company said, although implementing its advice will be difficult as there is no rapid test to determine if someone has had the disease.
The news magazine Proceso reported last week that researchers from the INSP reached a similar conclusion about the vaccine two years ago.
In a study published in November 2015, the researchers recognized the merit of the vaccination but warned that “the potential of this vaccine increasing the risk of severe dengue and other forms of dengue that require hospitalization is more than theoretical.”
They urged the Mexican government to postpone approval of the vaccine until more robust evidence about its safety was available, advice it seemingly didn’t heed.
Proceso also reported that another high-level official involved in the process to approve the vaccine had previously worked as a scientific director for Sanofi.
The vaccine has been shown to be 66% effective in all people over the age of nine and 81.9% effective in those over the same age who have previously been infected with the disease, also known as breakbone fever.
Despite the risks, experts argue that the vaccine is too valuable to be abandoned altogether, but the World Health Organization (WHO) has recommended that it only be used in places where there is a high incidence of dengue.
The mosquito-borne disease causes high fever, headaches, vomiting and muscle aches and is endemic in more than 100 countries, according to the WHO. Dengue affects millions of people annually and causes around 20,000 deaths.
However, unlike the Philippines, in Mexico there has been no widespread immunization project using the questionable vaccine.