Nadenggoy sa Dengvaxia

There are four strains of the dengue virus or serotypes. A person who has been infected by at least one of these strains (seropositive) stands a better chance of benefiting from vaccination compared to one who has never been infected (seronegative). That is why prior to any mass vaccination program, seroprevalence studies need to be conducted.

The World Health Organization (WHO) recommends that for a program to be impactful and cost-effective, “the prevalence of prior infection with dengue virus of any serotype, as measured by seroprevalence, should be approximately 70% or greater in the age group targeted for vaccination.”

It stated in a paper dated March 2016 that “there is a theoretical possibility that vaccination may be ineffective or may even increase that risk (of hospitalization due to dengue) in those who are seronegative at the time of first vaccination.”

WHO recommended, “Targeted studies, in parallel to vaccine implementation, are needed to address these questions, otherwise it will remain a controversial issue and could compromise public confidence in the vaccine program.”

The Philippine government in 2016 may have glossed over this in its haste to treat the scourge of dengue. More than 800,000 school children were immunized with dengvaxia, the world’s first dengue vaccine produced by Sanofi.

As foreshadowed by that WHO paper, the theoretical risk of hospitalization may have materialized with close to 3,300 individuals hospitalised and 62 child casualties, after receiving a dose of dengvaxia.

Khunsha Fatima and Najah Syed in the Journal of Global Health say that given dengue infection rates reach up to 90% in the Philippines, “at least 10% or around 80 000 of those children who do not have a prior history of dengue infection are now at an increased risk of developing severe dengue.”

I made a Freedom of Information (FOI) request back in December 2017 to see whether the government had performed seroprevalence studies in schools where it had conducted mass vaccination.

I asked whether such surveys were performed by, or on behalf of, the health department, and where. I also asked if government could provide the results of any surveys conducted, on the levels of seroprevalence of dengue recorded.

I got a response in September 2018 from Dr. Kenneth Ronquillo of the Department of Health. He said, “Your FOI request has been approved, however…as of the moment, this office can only provide you the data on our dengue morbidity monthly report from 2013 to 2018.”

I waited six months to see whether they could provide me with the data requested, to no avail. My sense is that if the government had done seroprevalence mapping, it would be able to release the results. The fact that they haven’t, shows that it probably wasn’t done.

Procurement documents I obtained from the DOH under a separate FOI request reveal that as part of the purchase of Php3 billion worth of dengue vaccines, Sanofi was meant to "conduct relevant training/orientation of health workers and teachers on the Dengue Vaccination Program" as well as "conduct orientation for parents, caregivers and students participating in the program".

When asked whether this was conducted, no reply was forthcoming.

The sad part is, people are still dying from dengue. The same morbidity reports, to which I was referred, state that in 2018 there were over 216,000 cases of dengue reported. This was 42% above the previous year, and higher than the five-year average. There were close to 1,100 deaths resulting from these cases.

Had the government taken the necessary steps in implementing a proper vaccination program, it could have determined which age groups and areas to involve. It could have properly informed parents of seronegative children of the increased risks of participating, in gaining their consent.

It is much harder to do that now, given the public panic following reported deaths due to dengvaxia. Fatima and Syed refer to this as “vaccine hesitancy” or a “delay in acceptance or refusal of safe vaccines despite the availability of vaccination services.”

In his public statements, former president Benigno “Noynoy” Aquino said he saw the risks of inaction outweighing the risks of action. Unfortunately, by acting in haste, without the proper precautions, he may have set us back a few years, at the very least, in the fight against dengue.