Immunogenicity of A/USSR (H1N1) subunit vaccine in unprimed young adults.

A clinical and serological study was performed on 267 of 636 volunteers vaccinated against Argentine hemorrhagic fever with the XJCl3 attenuated strain of Junin virus seven to nine years earlier, in order to determine their long-term evolution. This study included a clinical examination, a chest roentgenogram, an electrocardiogram, and the following laboratory determinations: white and red cell count, number of platelets, hematocrit, hemoglobin, sedimentation rate (Katz index), urea, nitrogen, glucose concentration, cholesterol, GOT, GPT, gamma GT, alkaline phosphatase, cholinesterase, and total bilirubin. Neutralization reactions were performed to determine presistence of antibody levels. All clinical and laboratory findings were within normal limits, excluding a long-term pathology attributable to the virus. Of 165 tested sera, 153 (90.3%) had detectable levels of neutralizing antibodies, and the rest had no antibodies after this time. Although these people live in the endemic area, it is considered that only the 9% that had increased antibody levels had suffered a reinfection during the seven- to nine-year period, which acted as a booster. This figure aproximately coresponds to the subclinical infection value found in the region. In the rest, the persistence of antibodies is attributed to the immunization achieved with the vaccine employed.