Is Brazil ready to face yellow fever?

Studies are in course to map the virus progression and anticipate vaccination in risk areas, avoiding the entry in these places

Associate Professor at the Infectious Diseases Department at São Paulo University Medical School (FMUSP), Marta Heloisa Lopes, reminds that Brazil is the worlds leading yellow fever vaccine manufacturer and, unlike what happened in Africa, in 2016, we are currently facing a wild yellow fever outbreak, not urban. We have conditions and we are developing, in São Paulo, studies to map and anticipate vaccination in risk areas, avoiding the virus entry in these places. People living near to or in touch with forest, rural or semi-urban areas, where wild transmissions vectors may be found, are being vaccinated, she says. Still according to the specialist, it is clear that public health services have problems, however, there are dedicated and committed teams working tirelessly to prevent and handle cases of the disease. We are introducing new therapy schemes, as liver transplant and testing antiviral drugs. We have many difficulties, but we are tackling this wild yellow fever outbreak, she adds.

Dr. Marta Heloisa, who is also the representative for the Brazilian Society of Tropical Medicine (BSTM) in the Immunization Advising Technical Committee (CTAI) at the Health Ministrys National Immunization Program (PNI), emphasizes the concern involving vaccination that generally, should be a routine and not restricted to eventual campaign moments. We have, in Brazil, a vaccination calendar that includes all ages. Safe and effective vaccines are distributed at no cost in the entire country, for the entire population. However, a large number of people, mainly adults, only seek basic health units, where the vaccines are given, in times when case numbers increase, as for example, influenza or currently yellow fever, and do not consider updating their vaccination schemes. Attention to prevention measures regarding diseases, among which vaccination, should be constant, and not sporadic, she warns.

Fractional doses have the same immunization capacity as the full dose

Despite the Brazilian government having stressed since the beginning that the yellow fever vaccines fractional dose had exactly the same immunization capacity as the full dose, there was a great speculation on the matter. In February, an article published in the New England Journal of Medicine had international impact while evidencing, again, that the fractional dose stimulates adequate immune response. The article by Ahuka-Mundeke and collaborators analyzed the response of 0.1mL of the vaccine in 716 people, older than 2 years-old, in Kinshasa, Democratic Republic of Congo, resulting in a 98% positivity after vaccination, meaning the dose was able to stimulate antibody response among the immunized people.

Dr. Marta Heloísa details that previous Brazilian studies had already demonstrated the immunogenicity and safety of fractional vaccine doses. Studies carried by Fiocruz researchers, published in 2013 (Martins RM et al. 17DD Yellow fever vaccine: a double blind, randomized clinical trial of immunogenicity and safety on a dose-response study. Hum Vaccin Immunother 2013; 9:879-88) and in 2014 (Campi-Azevedo et al. Subdoses of 17DD yellow fever vaccine elicit equivalent virological/immunological kinetics timeline. BMC Infectious Diseases 2014, 14:391), demonstrated that subdoses of the vaccine could be adequate for immunization, she signs.

The expert reminds that in an article published in 2016, Monath and collaborators, among them Dr. Reinaldo Martins, Brazilian researcher at Fiocruz, showed that using 0.1mL of the vaccine (fractional dose equivalent to one fifth of the standard dose), as a possible solution for supply. (Thomas P Monath, Jack P Woodall, Duane J Gubler,Thomas M Yuill, John S Mackenzie, Reinaldo M Martins, Paul Reiter, *David L Heymann. www.thelancet.com Vol 387 April 16, 2016).

Correct information help raise awareness of the population and adhesion to vaccination

The disclosure of correct information, without causing panic, help increasing the acceptance of the measures proposed by public health authorities. To Dr. Marta Heloísa, the disclosure, by different means of communication, including social networks, of correct information, building trust in the adopted measures, could effectively contribute to the populations trust, and consequently, greater adhesion to vaccination.

To the expert it is still too early to claim the vaccination campaigns, especially in Rio de Janeiro and São Paulo, focused in the fractional dose, are far from reaching the proposed goal. To her, vaccination is in course and new vaccination recommended areas are being added to those initially proposed. This strategy is based in studies performed in São Paulo, that map the virus progression in the so-called ecological corridors. This way, we propose vaccinating the population before the virus probable arrival. Besides this, we must continue what States and cities have been doing: vaccinating home after home in forest areas, with greater risk and difficult access to health services, she ends.…