Serologic studies on the behaviour of influenza virus type A in persons of Greater São Paulo during 1976, 1978 and 1979

Influenza vaccination in Brazil: rationale and caveats

Mass vaccination campaigns against influenza in the elderly have been conducted in Brazil since 1999. A search of the literature on influenza in Brazil indicated that data on disease burden are still scarce and inaccurate. Published data seem to indicate that vaccination has produced some impact in the southern and southeastern regions but not in other regions of Brazil. A discussion of the technical and scientific rationale for mass immunization against influenza is presented and it is argued that the current strategy has not taken into account potential differences in disease occurrence in different areas. It is suggested some epidemiological surveillance actions needed to address major concerns regarding mass influenza vaccination and its impact in Brazil.

[Seroepidemiological survey for influenza virus in Belém, Pará, Brazil, 1992-1993]

A seroepidemiological study was carried out from 1992 to 1993 to estimate the prevalence of antibody to prevailing influenza virus strains circulating among patients attending the IEC Virology Laboratory in Belem, Northern Brazil. A total of 179 (11%) of serum samples were obtained during the post-epidemic period and processed by the hemagglutination inhibition test against the A/Taiwan/1/86 (H1N1), A/Beijing/353/89 (H3N2), and B/Yamagata/16/88 types of influenza virus. The serological results indicate circulation of viruses antigenically related to all three strains during the two-year study period. In 1992, the overall prevalence rates of HI antibodies to H1N1 and H3N2 were 84% and 56%, respectively. Presence of antibodies to both strains was detected in all age groups, suggesting intense viral activity that year. Antibodies to influenza B were detected at lower levels in all patients during this period. Similar prevalence to the H1N1 virus was noted in 1993, indicating that this strain occurred in both years. However, an increase in prevalence rates for the H3N2 virus was seen in 1993, suggesting that this strain (or a related virus) circulated intensively during this year. Influenza B activity also increased in 1993, causing infection mainly among young adults.