“This is up from the 24,000 cases in the same period in 2018. So we do see significant increase in dengue cases,” Weiler says. He warned of a “high dengue caseload year” in 2019.

Again, children are vulnerable and those who have been infected by dengue previously run a higher risk of dying from a second bite from an Aedes aegypti mosquito, which transmits the virus. Complicating matters, Weiler says, is a controversy surrounding the Dengvaxia dengue vaccine, the world’s first, produced by French manufacturer Sanofi Pasteur.

The health department and public health advocates in the Philippines blamed the recent measles outbreak on a massive health scare over Dengvaxia, the once-promising dengue vaccine introduced by the government three years ago. The Dengvaxia dengue vaccine is thought to have caused 10 deaths, and has convinced Filipino parents not to give their children a measles shot despite the recent outbreak.

The Philippines’ Department of Justice announced this month that it has grounds for indicting existing and former Sanofi Pasteur executives, and local health officials, over the 10 deaths suspected of being caused by the company’s vaccine.

Today the dengue vaccine is no longer available in the country. The controversy over Dengvaxia began in April 2014, when Sanofi Pasteur announced that an efficacy study showing that administering the vaccine in Asia had a “significant reduction of 56 per cent of dengue disease cases”.

Based on the favourable results of this study, the Department of Health in the Philippines launched a dengue vaccination campaign in Metro Manila and two other regions on Luzon Island in April 2016. Some 700,000 people received at least one dose of the vaccine, with the Philippine government paying 3.5 billion pesos (US$66.6 million) for the stock.

Development of the vaccine, which took 20 years, had been challenging because to be effective it must target all four variants of the dengue virus. A second infection, of a different strain, is often fatal.

When two children who had been given a Dengvaxia shot died, the Philippine House of Representatives convened its committee on health to open an investigation into the vaccine. In November 2017, Secretary of Health Francisco Duque – appointed by President Rodrigo Duterte after his 2016 election victory – suspended the Dengvaxia vaccination programme.

Weiler says there has been “a lot of political noise from all sides” about Dengvaxia, and that had made it difficult to relay evidence-based public health information essential to battling the recent measles outbreak. “It made things complicated, certainly for parents to find out what the situation is,” he says.

The WHO’s Strategic Advisory Group of Experts on Immunisation, in a Weekly Epidemiological Report in June 2018, stated that “for individuals who have not been previously infected by the [Dengvaxia] dengue virus, vaccination should not be recommended”.

A spokesman for Sanofi Pasteur told the Post earlier this month that the Philippine Food and Drug Administration (FDA) revoked the certificate of product registrations of Dengvaxia “for the alleged failure of Sanofi Pasteur to comply with post-marketing authorisation requirements”.

The company insists that the FDA had made the decision to revoke its product “despite our diligence, including the submission of documents from completed post-approval commitments and regular updates on the status of post-marketing studies”.

It has filed a motion requesting the FDA to reconsider its order, the spokesman said. “It is important to note that the Philippines FDA is not questioning the safety and efficacy of Dengvaxia, which is consistent with the WHO’s position on the vaccine and also with the recent decision to grant market authorisation for the use of Dengvaxia in Europe,” the spokesman said.

The United States Food and Drug Administration’s Vaccines and Related Biological Products Advisory Committee on March 7 put the safety and effectiveness of the dengue vaccine to the vote, the spokesman added.

“In people nine to 17 years of age, the committee voted favourably on effectiveness [13 to one] and safety [10 to four]. In people nine through to 45, the committee voted six to seven [with one abstention] on effectiveness and seven to seven on safety. We are continuing to work closely with the FDA, which is expected to make its decision [on whether to license the vaccine] by May 1, 2019,” the spokesman said.

The clinical trials conducted by Sanofi Pasteur, involving more than 40,000 people in 15 countries, “indicate that the vaccine’s safety profile is satisfactory across age groups for those with previous dengue infection at the time of vaccination”, the spokesman insisted.

Asked about the Philippine Department of Justice’s announcement it has grounds to indict existing and former Sanofi officials, the spokesman said: “We strongly disagree. We will vigorously defend them. There is no clinical evidence that any reported fatalities were causally related to vaccination.

“We diligently monitor the safety of people participating in clinical studies. We are also continuously monitoring the safety profile of the vaccine in a real-world setting, including the Philippines.”

Facing accusations of corruption over his administration’s purchase of the vaccine, former Philippine president Benigno “Noynoy” Aquino said in a Facebook statement in February that his then secretary of health, Enrique Ona, sent him a memo in August 2010 informing him that cases of dengue fever had been on the rise in the country. In briefings, Ona had told the president about a vaccine that was “under development”.

Aquino wrote that following Sanofi Pasteur’s announcement of the results of Dengvaxia clinical trials in 2014, he authorised the country’s health authorities to “ensure the vaccine would go through the whole meticulous process [of approvals] and diligently prepare as soon as possible so that all our nationals could benefit from the vaccine”.

Philippine Vice-President Leni Robredo told the Post during a visit to Hong Kong on March 10 that apprehension and fear among Filipinos about having a measles shot was due to the “irresponsible opposition against Dengvaxia”.

“For me, it is OK to criticise if there is really an issue. But it should not have led to ordinary citizens being scared away from a proven vaccine against measles,” she said.

The WHO’s Weiler says the Philippines should increase its measles vaccination rate to “this magic figure of 95 per cent” to curtail the spread of the disease and prevent further outbreaks. Some 2.6 million children in the country are still unvaccinated or not fully vaccinated against measles, given the “suboptimal” vaccine uptake rate of 80 per cent to 85 per cent.

Weiler is confident “we will be able to overcome the measles outbreak in the coming months”.

But, he says, “we should be prepared now before we see a pickup of dengue cases linked to the rainy season, and to prepare for a larger influx of patients needing treatment”.