Results of a two-year study of humoral immunity to influenza A and B viruses in children under the age of 14 years in Moscow and its suburbs.

A serological survey of antibodies to influenza A(H1N1), A(H2N2), A(H3N2) and B viruses was done with sera collected in Moscow in October 1980 and November 1981 from 542 children under 14 years of age. The results of the study showed convincingly that influenza A(H2N2) viruses were not circulating in Moscow in 1980-81. Low titres found in the sera from four young children were due to cross-reactions which were eliminated from the sera by absorption with A/USSR/174/79(H3N2) virus.

[Humoral immunity to influenza A and B viruses in the blood sera of children younger than 14 in 1981].

Blood sera from 317 children with the history of noninfectious diseases or normal children pretreated with RDE were collected and examined for antihemagglutinins to 7 influenza virus strains in order to check the results of studies of 1980 and to study the immunity status to influenza A (H1N1), A (H2N2), A (H3N2) and B in the preepidemic period of 1981. Negative results of antihemagglutinin detection to influenza A/Iksha/1/57 (H2N2) in sera of all the children have confirmed the conclusion made in the previous paper (1) that influenza A (H1N2) viruses have not circulated in recent years among the population of Moscow City and suburban areas. Fourteen sera positive in HI tests with A/Shklyawer/49 virus similar to A/PR/8/34 (H1N1) in titres from 1:20 to 1:40 did not produce hemolysis zones with A/PR/8/34 virus in RHT, but most of these sera gave similar results of both tests with A/Brazil/11/79 and A/Khabarovsk/1/77 viruses.

[Level of antibodies to influenza viruses A and B in the blood sera of children under 13].

The level of antibodies to influenza A (H1N1), A (H2N2), A (H3N2), and B viruses in the blood sera collected in October and November, 1980, from 224 children under 13 resident in Moscow and its suburbs was studied The results of the study showed convincingly the influenza A (H2N2) viruses did not circulate at that time among the population of Moscow and its suburbs. The 4 positive (not exceeding 1 : 40 findings in sera from younger children were due to the presence in them of the antibodies cross-reacting with A (H2N2) and A H3N2) viruses which could be completely eliminated from the sera by adsorption of the latter with A/USSR/174/79 (H3N2) virus. The A (H3N2) viruses were the main cause of ARD developing in children in July-September, 1980.

Investigation of the incidence of influenza A viraemia caused by virus strains circulating among children in 1968 - 1977.

Nineteen strains of Type A influenza virus isolated from the blood of small children in 1968--77 were studied. The investigation of the strains in HAIR with antisera to the antigenic components of the strains in HAIR with antisera to the antigenic components of the strains A/Hong-Kong/68,A/Anglia/72, A/Port Chalmers/73 and A/Victoria/75 made it possible to demonstrate antigenic "drive" of the haemagglutinin in the years 1968--1977 and to divide the strains into 4 varieties. A high sensitivity to inhibitors was observed in all the strains isolated.