Medical Rounds
VACCINATION AGAINST SWINE INFLUENZA TE-WEN CHANG, M.D
The swine influenza of 1918 has been called "The Killer Flu." Unfortunately, the real story of the pandemic is lost; the virus was not isolated until a decade later, and then from pigs, not men. This virus rarely infects man, but shares genetic markers with the New Jersey virus, the cause of the recent fatality at Fort Dix, New Jersey. This fatality does not necessarily mean that the New Jersey swine virus is more virulent than the A/Victoria strain. A sick soldier refused to rest in spite of flu, and collapsed during a night march. He died shortly thereafter of hemorrhagic pulmonary edema. The tracheal aspirate yielded swine influenza virus. During the same period in New Jersey, 21 other patients of all age groups died of pneumonia related to A/Victoria virus. None of these deaths received any public attention. The 1918 pandemic was associated with a high mortality involving many people aged 20-40. There is something peculiar about this pandemic. Not only was the mortality rate high among young people, but many cases of encephalitis with subsequent development of parkinsonism occurred. Fncephalitis persisted until 1926, when it abruptly ceased; curiously, it has not reappeared. This encephalitis epidemic also affected young people, unfortunately with a mortality of 30%. Possibly, a second viral agent was Address for reprints: Te-Wen Chang, M.D., Infectious Disease Service, New England Center Hospital, 171 Harrison Avenue, Boston, MA 02111.
613
From the Department of Medicine, Tufts University School of Medicine, Boston, Massachusetts
involved in the pandemic of 1918, but this has not been proved. Perhaps this modified the true picture of swine flu, which might not have differed from the subsequent pandemics of A2 and Hong Kong virus. Fach pandemic studied so far has been found to involve a period of several months of viral seeding before the outbreak.^ Without early viral seeding, it is unlikely that a pandemic will follow. Since the 1918 pandemic, the flu virus has undergone 4 major antigenic changes: AO (H0N1) in 1933, A l (H^INI) in 1946, A2 (H2N2) in 1957 and HK (H3N2) in 1968. Of these, only A2 and HK produced pandemics. With the others, only smaller epidemics appeared. On theoretical grounds, the ciiance of New Jersey swine virus developing pandemically is 50-50. If it does reach epidemic or pandemic proportions, we should be able to detect this tendency months ahead by the presence of early viral seeding in the population. A surveillance program (or virus watch program) by all major virus laboratories in the United States and elsewhere is an essential step toward a successful control of swine influenza. This approach is an attempt to deal with a serious problem from a scientific point of view rather than from an emotional reaction.
614
INTERNATIONAL JOURNAL OF DERMATOLOGY
If we follow the recommendation to initiate a vaccination program designed to immunize every adult as soon as the swine vaccine becomes available, what shall we do if swine flu starts a year or so later? Shall we wage another preventive war again, and again? To assure prolonged protection, one needs annual immunization. The flu vaccines are not without reactions. Low-grade fever and general muscle pains may occur in up to 20% of the vaccines. Children less than 5 may react even more commonly. In those under 3 years of age, febrile convulsions are known to occur.^ However, a recent trial with swine vaccine indicates that with small but sufficient doses of vaccine, the reaction rates in adults are negligible.^
October 1976
Vol. 15
high-risk groups as soon as it becomes available. These include patients with heart disease of any etiology; chronic bronchopulmonary diseases, such as asthma, chronic bronchitis, bronchiectasis, tuberculosis and emphysema; chronic renal disease; diabetes mellitus and other chronic metabolic disorders, and people 65 and over. (This represents a booster dose because over 90% of this population has antibodies against swine influenza virus from 1918.) Monovalent swine vaccine will be given to anyone requesting vaccination, and everyone except children and those sensitive to egg protein either by ingestion or by injection, as soon as indication of swine flu epidemic begins to appear.
Conclusion Immunization To avoid these uncertainties, it is reasonable to stockpile swine vaccine and not to begin a comprehensive immunization program, except for the high-risk groups, until there is some further reason to believe that there will be swine flu epidemic. For this reason, I would like to add 2 more words to the editorials in The New England Journal of Medicine by Weinstein and Ingelfinger: "Thou shalt be vaccinated when indicated."^- '^ Two preparations containing swine virus vaccine will be available soon: a bivalent containing swine and A/Victoria and a monovalent containing swine virus alone. A compromised approach is suggested. Bivalent vaccine will be given to all
Although the swine influenza of 1918 was catastrophic, we are not sure whether history will repeat itself. We now have antibiotics to combat bacterial complications, sophisticated medical facilities to care for sick patients and effective measures for prevention. It is unlikely that the dreadful epidemic of 1918 will be duplicated in the future. References 1. Kilbourne, E. D., Epidemiology of influenza. In the Influenza Viruses and Influenza. Edited by Kilbourne, E. D. New York, Academic Press, 1975. 2. Center for Disease Control: Influenza Surveillance. Report No. 90. February, 1976. 3. Weinstein, L., Influenza—1918, a revisit? N. Engl. J. Med. 294:1058, 1976. 4. Ingelfinger, F. J., Thou shall be vaccinated. N. Engl. J. Med. 294:1060, 1976.
VACCINATION AGAINST SWINE INFLUENZA TE-WEN CHANG, M.D
The swine influenza of 1918 has been called "The Killer Flu." Unfortunately, the real story of the pandemic is lost; the virus was not isolated until a decade later, and then from pigs, not men. This virus rarely infects man, but shares genetic markers with the New Jersey virus, the cause of the recent fatality at Fort Dix, New Jersey. This fatality does not necessarily mean that the New Jersey swine virus is more virulent than the A/Victoria strain. A sick soldier refused to rest in spite of flu, and collapsed during a night march. He died shortly thereafter of hemorrhagic pulmonary edema. The tracheal aspirate yielded swine influenza virus. During the same period in New Jersey, 21 other patients of all age groups died of pneumonia related to A/Victoria virus. None of these deaths received any public attention. The 1918 pandemic was associated with a high mortality involving many people aged 20-40. There is something peculiar about this pandemic. Not only was the mortality rate high among young people, but many cases of encephalitis with subsequent development of parkinsonism occurred. Fncephalitis persisted until 1926, when it abruptly ceased; curiously, it has not reappeared. This encephalitis epidemic also affected young people, unfortunately with a mortality of 30%. Possibly, a second viral agent was Address for reprints: Te-Wen Chang, M.D., Infectious Disease Service, New England Center Hospital, 171 Harrison Avenue, Boston, MA 02111.
613
From the Department of Medicine, Tufts University School of Medicine, Boston, Massachusetts
involved in the pandemic of 1918, but this has not been proved. Perhaps this modified the true picture of swine flu, which might not have differed from the subsequent pandemics of A2 and Hong Kong virus. Fach pandemic studied so far has been found to involve a period of several months of viral seeding before the outbreak.^ Without early viral seeding, it is unlikely that a pandemic will follow. Since the 1918 pandemic, the flu virus has undergone 4 major antigenic changes: AO (H0N1) in 1933, A l (H^INI) in 1946, A2 (H2N2) in 1957 and HK (H3N2) in 1968. Of these, only A2 and HK produced pandemics. With the others, only smaller epidemics appeared. On theoretical grounds, the ciiance of New Jersey swine virus developing pandemically is 50-50. If it does reach epidemic or pandemic proportions, we should be able to detect this tendency months ahead by the presence of early viral seeding in the population. A surveillance program (or virus watch program) by all major virus laboratories in the United States and elsewhere is an essential step toward a successful control of swine influenza. This approach is an attempt to deal with a serious problem from a scientific point of view rather than from an emotional reaction.
614
INTERNATIONAL JOURNAL OF DERMATOLOGY
If we follow the recommendation to initiate a vaccination program designed to immunize every adult as soon as the swine vaccine becomes available, what shall we do if swine flu starts a year or so later? Shall we wage another preventive war again, and again? To assure prolonged protection, one needs annual immunization. The flu vaccines are not without reactions. Low-grade fever and general muscle pains may occur in up to 20% of the vaccines. Children less than 5 may react even more commonly. In those under 3 years of age, febrile convulsions are known to occur.^ However, a recent trial with swine vaccine indicates that with small but sufficient doses of vaccine, the reaction rates in adults are negligible.^
October 1976
Vol. 15
high-risk groups as soon as it becomes available. These include patients with heart disease of any etiology; chronic bronchopulmonary diseases, such as asthma, chronic bronchitis, bronchiectasis, tuberculosis and emphysema; chronic renal disease; diabetes mellitus and other chronic metabolic disorders, and people 65 and over. (This represents a booster dose because over 90% of this population has antibodies against swine influenza virus from 1918.) Monovalent swine vaccine will be given to anyone requesting vaccination, and everyone except children and those sensitive to egg protein either by ingestion or by injection, as soon as indication of swine flu epidemic begins to appear.
Conclusion Immunization To avoid these uncertainties, it is reasonable to stockpile swine vaccine and not to begin a comprehensive immunization program, except for the high-risk groups, until there is some further reason to believe that there will be swine flu epidemic. For this reason, I would like to add 2 more words to the editorials in The New England Journal of Medicine by Weinstein and Ingelfinger: "Thou shalt be vaccinated when indicated."^- '^ Two preparations containing swine virus vaccine will be available soon: a bivalent containing swine and A/Victoria and a monovalent containing swine virus alone. A compromised approach is suggested. Bivalent vaccine will be given to all
Although the swine influenza of 1918 was catastrophic, we are not sure whether history will repeat itself. We now have antibiotics to combat bacterial complications, sophisticated medical facilities to care for sick patients and effective measures for prevention. It is unlikely that the dreadful epidemic of 1918 will be duplicated in the future. References 1. Kilbourne, E. D., Epidemiology of influenza. In the Influenza Viruses and Influenza. Edited by Kilbourne, E. D. New York, Academic Press, 1975. 2. Center for Disease Control: Influenza Surveillance. Report No. 90. February, 1976. 3. Weinstein, L., Influenza—1918, a revisit? N. Engl. J. Med. 294:1058, 1976. 4. Ingelfinger, F. J., Thou shall be vaccinated. N. Engl. J. Med. 294:1060, 1976.
