WASHINGTON, Oct. 2 (UPI) -- An analysis of 6 million people who received the smallpox vaccine in 1947 found no increase in deaths from heart problems, federal health officials said, which strongly suggests the vaccine did not cause the heart attacks and deaths reported earlier this year in civilians and military personnel.
The findings could help revive the nationwide campaign to vaccinate healthcare personnel against smallpox, which has stalled over concerns about the vaccine's serious side effects, such as brain swelling, a widespread skin infection and even death. Although the plan originally anticipated vaccinating about 500,000 people, fewer than 40,000 have been vaccinated to date.
"Our study supports a growing body of evidence that smallpox vaccine is not related to cardiac-related deaths," co-author of the study Dr. Susan Manning, with the Centers for Disease Control and Prevention's epidemic intelligence service, told United Press International. Manning is on assignment at the New York City Department of Health.
In the study, which appears in the Oct. 3 issue of Morbidity and Mortality Weekly Report, officials from the CDC and the New York Health Department looked at a smallpox outbreak in 1947 in which 6 million New York residents or 80 percent of the city's population were vaccinated in a four-week period.
The investigators saw no increase in deaths caused by heart problems when comparing death certificates from a two-week period after vaccination, when heart-related problems would be most likely to occur, to the same period in the previous year and the year after.
There also was no increase in deaths from myopericarditis -- an inflammation of the heart seen in 11 military personnel in 2003 -- going out to four weeks after vaccination. In addition, the investigators did not see a rise in mortality due to any cause among the vaccinees.
Although CDC officials were involved in the study and wrote in an editorial note in the journal that "the study casts doubt on the causal link between death caused by cardiac adverse events and smallpox vaccination," the agency now appears to be backing off drawing any firm conclusions.
"We want to look into this very deeply before we come up with any solution or recommendation," CDC spokesman Von Roebuck told UPI.
Since the smallpox campaign began in December, one member of the military and two civilian healthcare workers have died after suffering heart attacks following vaccination, but all were 55 or older and had a history of heart problems. Initially, that made it unclear whether the vaccine was to blame, but health officials now think the heart attacks were unrelated to the shot.
Five other civilians reported heart problems and non-fatal heart attacks. Of the more than 500,000 military personnel vaccinated, 37 have experienced heart inflammation, otherwise known as myopericarditis, which both the Department of Defense and the CDC now suspect can be caused by the vaccine. All 37 service members have recovered.
Roebuck noted from the inception of the smallpox campaign the CDC has placed a strong emphasis on safety and will continue to advise healthcare workers not be vaccinated if they have a history of heart disease or three or more risk factors for heart problems -- a provision put in place after the two civilians died from heart attacks.
The exclusions "will stay in place until we have resolved this investigation," he said.
A study by the DoD, which continues to vaccinate troops at a rate of 2,000 per week, concluded heart inflammation is a rare risk in people who receive the vaccine for the first time but it was not seen in personnel who previously had been inoculated.
Other heart conditions, such as heart attacks, do not appear to be linked to the vaccine as they do not occur at higher rates in vaccinees, DoD spokesman James Turner told UPI.
"DoD smallpox vaccinees are at no higher risk of other heart conditions than unvaccinated people," Turner said.
The civilian campaign has nearly come to a halt in many parts of the country as unions and hundreds of hospitals advised nurses, physicians and other healthcare workers to forego the shots because of the risks posed by the vaccine. In addition, there was a concern vaccinees could pose a risk to patients because the virus used in the vaccine -- which is not the smallpox virus but a closely related one called vaccinia -- can shed from people after inoculation and cause infections in other people.
This study could help persuade healthcare workers who were concerned about heart problems to get vaccinated, said Lorna Thorpe, an epidemiologist with the New York Health Department and a co-author of the analysis.
Thorpe noted New York hospitals are rolling out vaccination programs, conducting training and education sessions and planning for "a second wave of vaccination campaign to begin in 2004."
Other groups around the country continue to be reluctant to participate. Charles Idelson, spokesman for the California Nurses Association, said his group would continue to advise its members not to be vaccinated and anticipated other groups that opposed it would not change their position in light of this study.
"There was a massive revolt against this campaign by registered nurses and other healthcare workers across the U.S. and there's no reason to think any of that would change," Idelson told UPI.
Linda McDonald, a registered nurse and president of the United Nurses and Allied Professionals, which represents workers in Rhode Island, Vermont and Connecticut, had a similar reaction.
"We're still advising our members not to participate," McDonald told UPI.
Both McDonald and Idelson said the vaccination campaign is unnecessary because, as the 1947 event demonstrates, healthcare workers could be rapidly inoculated if there ever was a smallpox attack.
McDonald said vaccinations have virtually stopped in her area and "this is something not on our radars anymore."
Roebuck, however, said more healthcare workers continue to get vaccinated and some states, such as Florida and Texas, already have moved on to advanced stages of the campaign and are vaccinating police and fire personnel.
McDonald noted if health officials attempt to rekindle the vaccination campaign "UNAP as a union and other healthcare unions will certainly address this."