Aedes albopictus, commonly known as the Asian tiger mosquito has recently been identified in the Algarve, and is a potential carrier of various extremely unpleasant diseases. Image: Pixabay

Portugal “has new vaccine against all types of dengue”

Offers 80% efficacy over 12 months; “previous contact with virus not needed”

Portugal’s institute of hygiene and tropical medicine (IHMT) is plugging a new vaccine that protects against all types of dengue, “and does not require previous contact with the virus”.

“It is indicated for people who have or have not had infection and (can be taken) from four years old to 60 years old,” director of the institute Filomeno Fortes tells Lusa, stressing that dengue – spread by infected mosquitoes – is among the 10 principal global threats to public health, according to the World Health Organisation, and can be found in more than 125 countries.

By coincidence, Portugal is said to be at risk of outbreaks of dengue, zika and chikungunya this summer, largely because of rising temperatures.

As Filomeno Fortes explains, the previous vaccine could only be administered to people who had already had contact with the virus. This new one – approved in December by INFARMED – can be given to anyone (between ages of 4-60); promises 80% efficacy over 12 months, and a 90.4% prevention of hospital admission for the virus “up to four and a half years from vaccination”.

Says Fortes, it is administered in two doses, “with an interval of between one and three months”.

Right now, the vaccine is not on the national vaccination programme, but Fortes believes this could change if there are further outbreaks of dengue, as have been witnessed in Madeira.

“Supposing that here in Portugal, in Madeira, where we have Aedes aegypti (a mosquito that transmits dengue); where there have been dengue epidemics in the past – if we are facing a situation of risk of the epidemic reappearing, authorities should decide whether to vaccinate the population en masse and, if so, the SNS (State health service) should assume the costs”, he said.

Advantages of vaccinating whole population in determined areas where outbreaks occur

Fortes explains what he perceives as the advantages of mass vaccinations: “The mosquito bites the person and introduces the virus into the blood. The antibodies (if the person is vaccinated) prevent the effect of the mosquito from damaging that organism, but that person, while infected, (…) if bitten, can infect another mosquito that, in turn, can transmit the virus to other people”.

In other words, in Fortes’ mindset, unvaccinated people could unwittingly act as conduits for the virus to propagate.

“He also stressed that the mosquito, once infected, always remains infected and that the eggs it lays, when they hatch, will hatch with infected vectors”, explains Lusa.

Symptoms may be initially mistaken for flu

From the public health point of view, Fortes “insists on the need to increase literacy regarding the disease, reminding both the population and health professionals that symptoms may initially be confused with those of a flu” (that is, if people develop symptoms. According to the WHO, “most people who get dengue won’t have symptoms. But for those that do, the most common symptoms are high fever, headache, body aches, nausea and rash. Most will also get better in 1-2 weeks.)

Maintaining surveillance and vector control measures is another priority for Fortes – especially where the Aedes albopictus mosquito (in continental Portugal) and Aedes aegypti (in Madeira) have already been detected – as well as permanent epidemiological surveillance.

The specialist also points to the need to have “diagnostic capacity”, recalling that there is a rapid detection test that can be used by any doctor to test for infection, and this should be freely available in health centres.

If there is a confirmed case of dengue – he adds – certain types of medication should be avoided, “as they may interfere with the patient’s haemorrhage”.

At IHMT, Filomeno Fortes explains, the indication is for travellers going to areas where dengue is endemic to be vaccinated at least two weeks beforehand.

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