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Current Trends Update on Influenza Activity Worldwide and World Health Organization and United States Recommendations for Influenza Vaccine Composition for the 1987-1988 Season

During February or March each year, the World Health Organization (WHO) summarizes available data on recently isolated influenza viruses around the world and issues recommendations for vaccine composition. The WHO reports (1,2) and the U.S. recommendations for composition of the 1987-1988 influenza vaccine are summarized below. Influenza--Worldwide

From September 1986 through February 1987, influenza A(H1N1) viruses predominated and, in most countries, were the only type of influenza virus isolated. As in previous epidemics since 1977, influenza A(H1N1) outbreaks occurred mainly among children and young adults. Few influenza A(H3N2) or influenza B viruses have been isolated.

Influenza A(H1N1). In the Americas, localized outbreaks occurred in the United States in October and November 1986. Influenza activity increased markedly in the United States in December, and, by mid-February, the virus had been isolated from patients in 49 states and the District of Columbia. Canada also reported activity from October through January. In Jamaica, outbreaks were serologically confirmed in both October and November. Brazil reported a single case in October.

In Asia, widespread outbreak activity was reported in the Democratic People's Republic of Korea during October and November and in Japan during November and December. China reported sporadically occurring cases from November through January, and Hong Kong reported them in December. In the Middle East, influenza A(H1N1) virus was isolated during outbreaks in the Islamic Republic of Iran in November and in Israel during November and December.

In Europe, localized outbreaks occurred in the United Kingdom in September and October, with continued activity through January. In both the German Democratic Republic and the USSR, outbreak activity was widespread during November and declined during December. Czechoslovakia, Hungary, Poland, and Yugoslavia also reported widespread influenza activity in December. Elsewhere in Europe (Denmark, the Federal Republic of Germany, Finland, France, Italy, the Netherlands, Norway, Romania, Spain, Sweden, and Switzerland), there was activity between December and February.

Influenza A(H3N2). Influenza A(H3N2) virus was isolated along with influenza A(H1N1) during an outbreak in the Democratic People's Republic of Korea. The virus was also isolated during an outbreak in Ecuador in November. Otherwise, A(H3N2) was detected only in sporadically occurring cases in Canada, China, Italy, Romania, Tunisia, the United States, and the USSR.

Influenza B. Outbreaks of influenza B were reported in Panama in September and October and in Singapore in December. Sporadically occurring cases were also detected in Canada, Chile, the Federal Republic of Germany, Hong Kong, India, Senegal, Singapore, Spain, Sweden, Taiwan, the United Kingdom, the United States, and the USSR. Antigenic Analysis of Recent Isolates

Influenza A(H1N1) viruses collected from many parts of the world during the 1986-1987 season have been antigenically characterized. Virtually all of them were indistinguishable from the A/Taiwan/1/86-like strains isolated in Asia early in 1986 (3). Influenza B viruses, which were isolated infrequently during the 1986-1987 season, were antigenically heterogeneous. However, all were closely related to B/Ann Arbor/1/86 (4).

The influenza A(H3N2) viruses isolated from outbreaks in all parts of the world during the 1985-1986 season were antigenically heterogeneous. About two-thirds differed from A/Mississippi/1/85 (H3N2), which was included in the 1986-1987 U.S. trivalent influenza vaccine. More than 25% of the A(H3N2) isolates characterized in the United States during the 1985-1986 season were antigenically similar to the A(H3N2) variant, A/Stockholm/8/85. Sera from recipients of the 1986-1987 trivalent vaccine were tested for antibody against both A/Mississippi/1/85 and A/Stockholm/8/85 antigens by hemagglutination inhibition (Table 1). For both young adults and nursing home residents who had received the trivalent vaccine, the geometric mean titers were nearly threefold lower to the A/Stockholm/8/85 virus than to the homologous A/Mississippi/1/85 virus. Furthermore, for the nursing home residents, 38% of the post-vaccination sera had titers that were greater than or equal to 40 to A/Stockholm/8/85, whereas 69% had titers greater than or equal to 40 to A/Mississippi/1/85.

Very few A(H3N2) viruses have been isolated during the 1986-1987 season; however, several appear similar to the A/Stockholm/8/85 variant. The 1986-1987 variant, A/Leningrad/360/86, an egg isolate suitable for vaccine production, appears closely related to A/Stockholm/8/85 (Table 2). These reference strains are poorly inhibited by ferret serum to the A/Bangkok/1/79 strain, used in influenza vaccines during the period 1980-1985. They are also inhibited at significantly reduced titers (compared to the homologous titer) by ferret antiserum to A/Mississippi/1/85. However, ferret antisera to both A/Stockholm/8/85 and A/Leningrad/360/86 inhibit A/Mississippi/1/85. Recommendations for the Composition of Influenza Virus Vaccines

Because of these antigenic variations and the continued isolation of viruses resembling A/Stockholm/8/85, WHO recommends that influenza vaccines for use during the 1986-1987 season contain a representative of this variant in place of A/Mississippi/1/85.

The above findings were discussed at a WHO meeting in February. The Public Health Service Vaccine Advisory Panel (PHSVAP) met during the same period to review the data regarding antigenic variations of virus isolates. Consistent with WHO recommendations, the PHS recommends that influenza vaccines for use in the 1987-1988 season be trivalent and contain the following antigens:

A/Taiwan/1/86(H1N1)-like antigen B/Ann Arbor/1/86-like antigen A/Leningrad/360/86(H3N2)-like antigen Recommendations of the Immunization Practices Advisory Committee regarding dosage and schedule of the vaccine will be published in the MMWR later this spring. Reported by: Influenza Research Center, Baylor College of Medicine, Houston, Texas. FL Ruben, MD, B Heisler, P Fallon, Montefiore Hospital, University of Pittsburgh School of Medicine, Pennsylvania. National Influenza Centers, Microbiology and Immunology Support Svcs, WHO, Geneva. Div of Virology, Office of Biologics, Food and Drug Administration. WHO Collaborating Center for Influenza, Influenza Br, Div of Viral Diseases, Center for Infectious Diseases, CDC.


  1. World Health Organization. Recommended composition of influenza virus vaccines for use in the 1987-1988 season. Wkly Epidem Rec 1987;62:54-7.

  2. World Health Organization. Recommended composition of influenza vaccine for use in the 1987-1988 season--a supplementary statement. Wkly Epidem Rec 1987;62:90.

  3. CDC. Antigenic variation of recent influenza A(H1N1) viruses. MMWR 1986;35:510-2.

  4. World Health Organization. Recommended composition of influenza virus vaccines for use in the 1986-1987 season. Wkly Epidem Rec 1986;61:61-4.

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