More than 733,000 elementary schoolchildren in the Philippines had been given Dengvaxia, the world’s first dengue vaccine, before Manila’s department of health stopped its use.
Its French pharmaceutical manufacturer Sanofi Pasteur warned that the jab may trigger more severe symptoms in those who had not been infected.
Sanofi Pasteur said Dengvaxia provided persistent protective benefit for those who previously suffered from dengue. The jab prevented severe illness for at least 30 months among those previously infected, according to the World Health Organisation.
Dengue, which is blamed with lowering economic productivity across the tropics, is the world’s most widespread mosquito-borne disease with nearly 400 million people infected every year.
Sanofi Pasteur said: “For those not previously infected by dengue virus, however, the analysis found that in the longer term, more cases of severe disease could occur following vaccination upon a subsequent dengue infection.”
The Philippines was the first country in the world to use the vaccine.
Health advocates in the Philippines expressed concern about Dengvaxia when the government announced in April 2016 that it would be used in schools despite being a new drug with unknown possible effects. But the government continued, budgeting about US$70 million for the programme.
Health ministry spokesman Eric Tayag told ABS-CBN television that the authorities were “prepared for a worst-case scenario” and those injected were being “followed up for adverse effects following immunisation”.
Tayag said the vaccine was exclusively given to nine-year-olds and older and the immunisation scheme only operated in areas where dengue was already widespread.
Hospital records were being checked for severe cases, he added.
Sanofi had reported that it could take around five years for severe dengue cases to become evident, Tayag added.
Spread by mosquitoes, dengue can cause a fever, intense headaches, muscular and joint pain and, in more severe cases, a swollen stomach, vomiting blood, bleeding gums and respiratory difficulties.
There are four dengue viruses, or serotypes, and most people who are infected recover and develop immunity to the first serotype they contracted. A later infection with a different serotype can sometimes lead to a severe hemorrhagic fever. About 25,000 people die globally every year from hemorrhagic fevers arising from the disease.
Manila said there were more than 1,000 deaths caused by the disease and around 211,000 suspected infections in 2016.
The Philippines is badly affected by dengue. Picture credit: Flickr