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Virus isolation attempts were made with nasopharyngeal secretions from 400 apparently healthy 0-5-year-old children of a semi-closed community. Repeated virus isolations were achieved in 25 cases subjected to periodic investigations in 1982-83. One-two reisolation(s), 1-5 months apart, of the initially detected viral agents could be obtained in 15 out of the 25 children. The following viruses were reisolated (in decreasing order of frequency): adenoviruses, respiratory syncytial virus, Coxsackie B1 virus, herpes virus type 1, parainfluenza virus type 3. The problems raised by the carriage of respiratory viruses in the nasopharynx of apparently healthy children are discussed.

Virus isolation attempts were made with 500 nasopharyngeal secretion samples from apparently healthy schoolchildren aged 7-14 years, vaccinated by nasal route with an inactivated influenza vaccine and with 500 samples from unvaccinated schoolchildren of the same age. The number of virus isolates obtained was much smaller in the former than in the latter group (13 as against 50 virus isolates). The role of influenza vaccination in the protection of schoolchildren against respiratory tract infections is discussed.

A number of 92 viral agents could be isolated from 1,000 nasopharyngeal secretion samples collected from apparently healthy schoolchildren aged 7-14 years. The following viruses were identified, in decreasing order of frequency: 42 influenza A/USSR 90/77 (H1N1), 20 adeno-, 20 parainfluenza, 8 Coxsackie B1 and 2 herpes virus strains.

The NIVGRIP inactivated influenza vaccine prepared in the "Stefan S. Nicolau" Institute of Virology was administered by oral route to 3-6-year-old children of a preschool community in October 1981, 1982 and 1983. There were no cases of acute respiratory tract infection (ARTI) in the community in the winter seasons of 1981-82, 1982-83 and 1983-84, with the exception of 3 ARTI cases recorded in February 1982 in unvaccinated children. In a similar community where no vaccination had been performed morbidity by ARTI was of 20% in 1982-83 and 12.6% in 1983-84. The efficiency and the advantages of oral influenza vaccination are outlined.

Influenza vaccinations were performed either by administration of a bivalent A2 + B vaccine, or by successive application of monovalent B and A2 vaccines. During an influenza epidemic caused by an A2 strain, the following observations could be made: a) the best efficiency (no influenza cases) was recorded in adults and aged persons (over 65 years) irrespective of the vaccination scheme; b) in schoolchildren the best results (no influenza cases) were obtained in the lot having received monovalent A2 vaccine, and in the lot vaccinated nasally with monovalent B vaccine and 14 days later with monovalent A vaccine.

At the beginning of the 1977--1978 schoolyear 10% standard gammaglobulin (0.03 ml/kg body weight) was administered to 974 preschool children and 530 schoolchildren. Representative groups of children were tested serologically and virologically before gammaglobulin administration and 3 months afterwards. No statistically significant reductions of viral hepatitis morbidity were recorded in the protected groups as against controls.