The three deaths in Pittsburgh on the eleventh day of the swine flu programme were the first test of the surveillance system the Center for Disease Control had built for it, and the only one it passed to everybody’s satisfaction. The CDC’s own account of the investigation was published in its Influenza Surveillance Report for the 1976 to 1977 season, with a shorter version in the Morbidity and Mortality Weekly Report of 22 October 1976. This piece follows the surveillance report’s reconstruction, which was written by the Pennsylvania state epidemiologist’s office and the programme’s staff from the clinic’s incident logs, the consent forms, the emergency-room logs of nearby hospitals, interviews with eleven clinic staff, and telephone calls to the next of kin.

The clinic

The Allegheny County Health Department’s clinic opened at 9:30 on the morning of Monday 11 October. A queue had already formed; people waited ten to thirty minutes. No rain fell; the temperature ran from 43 to 60 degrees Fahrenheit. By the time the clinic closed at 3:30 in the afternoon, “when there was no longer any demand for vaccination,” 1,242 people had received one of two lots of bivalent vaccine, swine and Victoria together, from the same manufacturer: 1,000 doses from Lot A and 242 from Lot B. The vaccine was given by ordinary needle and syringe, half a cubic centimetre through a 25-gauge needle, not by jet injector.

The nurses’ incident logs recorded three medical emergencies.

At 10:15 a 64-year-old woman turned pale and complained of dizziness. An emergency rescue vehicle was called and arrived in about ten minutes. She refused to be taken to hospital and was driven home at 11:00. When the field investigators reached her on 13 October she was in apparently good health.

At 10:55 a 77-year-old woman with previously diagnosed arteriosclerosis said she felt weak seconds after her vaccination. The nurse found her pale and blue and short of breath, sat her in the waiting area and gave her oxygen. The rescue vehicle was called again and came in ten minutes. At the hospital she was found to have acute pulmonary oedema, suffered a cardiac arrest despite treatment, and was pronounced dead at 12:10. The cause of death on the certificate was arteriosclerotic cardiovascular disease and coronary artery insufficiency, confirmed at autopsy.

At 11:10 an 83-year-old woman with a history of angina was vaccinated and seated in the waiting area about six feet from the second woman. As she watched the nurses and the rescue team working, she too felt faint. She was helped to a cot, given oxygen and a blanket, and the emergency team was called a third time. At another hospital her electrocardiogram was normal; she was discharged at 2:15 that afternoon and was in good health on 13 October.

Two other people vaccinated that morning, apparently without incident, died later in the day.

A 71-year-old man with a history of arteriosclerotic cardiovascular disease was vaccinated at 11:15. His wife was vaccinated too, and at 11:30 they left to shop in a nearby supermarket. While shopping he complained of pain in both arms. They went home and he went upstairs to rest. At about 12:45 he was found apparently dead, and was pronounced dead by his family physician at 1:30. Autopsy: acute myocardial infarction, with thrombosis of the right coronary artery and severe arteriosclerotic vascular disease.

A 73-year-old woman with heart disease and emphysema arrived at the clinic at 11:25 with her son-in-law. As they arrived, an emergency vehicle pulled onto the pavement and two medical staff went inside. While she stood in line, they came back out from behind the screen pushing a stretcher, and the queue broke to let it pass. She and her son-in-law were vaccinated at 12:15. She was driven home, ate lunch, went to her room to watch television, and was found dead at 6:30 that evening. Autopsy: acute myocardial infarction.

All three who died had received Lot A.

The investigation

The county health department closed its programme the next day, and the CDC’s investigators arrived. They took a ten percent random sample of the consent forms and telephoned the people on them on 12 October: 83 who had received Lot A and 50 who had received Lot B. Each was asked whether they had had a reaction, whether it had needed bed rest or a doctor, and what it was like. The reactions reported “were well within the limits reported in the national studies that found 1%-3% of recipients with minor reactions.”

Lot A had not been confined to Pittsburgh. Between 8 and 11 October, 5,750 doses of it had been given in the Westmoreland County clinics and 8,450 in Washington County, and no adverse reactions had been reported in either. Across 65 Pennsylvania counties, 77,000 doses of Lot A had been given on 11 October to people over 65. The empty and full vials from the Pittsburgh clinic went to the Bureau of Biologics in Bethesda, where every safety and sterility test was repeated; “no irregularities were found in the vaccine tested.” The emergency-room logs of the nearby hospitals for 11 October showed nobody else treated after a vaccination. The clinic’s procedures matched the programme’s guidelines, and “no irregularities were noted in the conduct of this clinic or in the technique for administering the vaccine.”

Then came the arithmetic the surveillance centre had prepared for. “Before the National Influenza Immunization Program was initiated, statistical summaries of major medical events were prepared at the Center for Disease Control. In anticipation of the occurrence of common major medical events such as stroke and myocardial infarction only temporally related to vaccination, the expected number of deaths per 24-hour period for stroke and myocardial infarction was computed for each age group by using National Center for Health Statistics mortality data.” The same rates had been worked out from Pennsylvania’s own vital statistics for 1973. Four people over 65 who had received Lot A on 11 October, the three in Pittsburgh among them, had died within 24 hours: a rate of 5 per 100,000 per day. The expected death rate for that age group in Pennsylvania, from the state’s own tables, was 17 per 100,000 per day. “Thus, no excess mortality occurred in vaccinees in this age group who received Lot A.”

That left the coincidence of three deaths from one hour at one clinic, which the investigators judged improbable on its own, and for which they offered an explanation: “it was postulated that the deaths of 1 or more of these 3 persons may have been related to stress involved in observing the medical emergency procedures described above. Interviews with next of kin in Cases 4 and 5 revealed that the persons concerned were in the clinic and had watched as at least 2 persons were taken out on stretchers.”

The count

The MMWR of 22 October put the Pittsburgh deaths in the national frame. As of 18 October, 41 deaths had been reported to the CDC in people whose illness began within 48 hours of an influenza shot; as of 13 October, more than two and a half million people had been vaccinated. The 41 had received thirteen lots of vaccine from all four manufacturers, were aged from 34 to 96 with a mean of 70.9, were all chronically ill, and had died in more than half the cases of myocardial infarction. “To date no deaths have been causally related to influenza immunization. The number reported is less than one-fourth the number anticipated to be coincidentally associated on a statistical basis.”

The number itself had a history. Donald Millar of the CDC had told the press on 13 October that “among people 70-to-74-years of age something on the order of 10 to 12 deaths per 100,000 such people will occur every day … We are seeing people who are dying within a day or so after vaccination. We expected to see that.” Neustadt and Fineberg, who quote him, thought these were figures “he might better have provided in advance,” and that the whole week, “the coincident deaths in some city, the wire services, the nearby mini-cameras, the eager coroner,” should have been foreseen and the states briefed for it. “Temporally related deaths,” they found, “were certainly anticipated in Hattwick’s surveillance center. We understand that they had been discussed from time to time at higher levels. The problem loomed, but that was all; planning was discounted on the ground that information spreads, and to alert the public might reduce the numbers willing to be immunized.” The county coroner, Cyril Wecht, had given the autopsy results on two of the three on 13 October, heart failure, and then hinted at negligence rather than coincidence: “We know that substances injected into the vascular system directly produce a more exaggerated and certainly a more rapid reaction than when those same substances are injected into the body fat or muscle mass.”

On 14 October, with the laboratory results in and the President vaccinated on television, Allegheny County and five of the nine states that had suspended resumed, and the other four said they would. During the week of the deaths 2.4 million people were vaccinated, and Pittsburgh went on to vaccinate nearly 43 percent of its adults, one of the highest rates of any large city.

Sources

• Center for Disease Control, Influenza Surveillance Report No. 92, September 1976-June 1977, issued 1981, section on adverse reactions: “Investigation of Deaths Following Influenza Vaccination–Allegheny County, Pennsylvania,” reported by William Parkin, acting state epidemiologist, Pennsylvania, and the National Influenza Immunization Program. The sequence of events, the five cases, the telephone survey, the other counties, the Bureau of Biologics tests, the expected death rate of 17 per 100,000 and the next-of-kin interviews. CDC Stacks. stacks.cdc.gov
• Center for Disease Control, Morbidity and Mortality Weekly Report 25, 22 October 1976, “Influenza–United States,” for the 41 deaths as of 18 October, the lots, the ages and “less than one-fourth the number anticipated.” CDC Stacks. stacks.cdc.gov
• Richard E. Neustadt and Harvey V. Fineberg, The Swine Flu Affair: Decision-Making on a Slippery Disease, U.S. Department of Health, Education, and Welfare, 1978, chapter 9, “Starting and Stopping,” for Wecht, Millar, Cronkite and the authors’ judgement; the quotations from Wecht and Millar are from CBS transcripts as the report gives them, and are at second hand here. archive.org