Spike in Dengue Cases Underlines the Crucial Role of Vaccination

The number of dengue cases in Brazil has already reached 217 thousand in 2024, representing almost five times the total calculated in the same period last year. To date, there are 15 confirmed deaths and 149 deaths under investigation. In this sense, the government announced a vaccination campaign against the disease, scheduled to begin in early February, which includes around 500 municipalities in 16 states and has a target audience of teenagers between 10 and 14 years old.

Professor Marcos Boulos, from the Department of Infectious and Parasitic Diseases at the Faculty of Medicine (FMUSP) of the University of São Paulo, comments on the increase in cases of the disease in Brazil and provides information about this vaccination.

Causes of dengue

According to the professor, an increase in dengue fever occurrences in the summer season is normal, as the number of rains and puddles of water that help the reproduction of the Aedes aegypti mosquito increases . However, possible phenomena caused by El Niño (intense rain and excessive heat) increased these factors, causing a larger epidemic, which has not occurred since 2019 — the expert says that, every four or five years, there is an explosion of a new type of dengue, causing new serotypes.

“The disease provides permanent immunity for each type of virus, and we have four. We had type 1 circulating for a long time, and people start to become immune, but, suddenly, when someone else comes, the disease starts to increase more than we expected”, says Boulos. The doctor also adds that the disease itself is not serious, but the delay in receiving care or seeking the procedure in some cases, in addition to a possible lack of preparation by specialists, increases the severity of dengue.

Vaccination against the disease

The Ministry of Health announced, at the end of last year, the incorporation of the Qdenga dengue vaccine, purchased from the Takeda Pharma laboratory, into the Unified Health System (SUS), but the need for double doses and the low number of vaccines available made the government define a target audience: teenagers aged 10 to 14, a group that is highly susceptible to the disease. Other foci are regions with high transmission of type 2 disease.

“It should be used in regions where there are more cases of dengue, because the vaccine is more effective when people have already had a serotype of dengue, it reduces the severity of the disease. So, for this reason, the Ministry of Health is prioritizing the places where the endemic disease occurs every year”, explains Boulos. He also adds that, due to these factors, the vaccine is not recommended for use in the city of São Paulo, even with a large increase in the number of dengue occurrences.

The professor also comments on the vaccine being developed by the Butantan Institute, which will be applied in just one dose and has shown to be very effective. According to data from the institute itself, Butantan-DV showed almost 80% efficacy in preliminary results from the third phase of clinical studies. In people who have already contracted the disease, prevention can reach close to 90%, but the number drops to approximately 70% in cases of first contact with the virus.

Other solutions

Despite the importance of vaccines, the professor believes that the real solution is to avoid mosquito breeding sites, with stagnant water inside the population’s homes or backyards. Boulos also says it is important to remember that Aedes aegypti is an urban vector, unlike some other diseases caused by insects.

The doctor also adds to the importance of training human resources to care for the population in cases of dengue fever. “As it is not a serious disease, you can quickly treat those few who arrive with greater severity and then the disease is controlled”, explains Boulos. He also cites the need for annual training, as there is a lot of change in the place of care among trained professionals, and they can be replaced by people who are not used to the disease. “So, the most important thing, in addition to all the work we do to avoid breeding sites, is that professionals are trained in caring for patients, who will certainly come in greater numbers at this time”, he concludes.