It’s flu season again, which means that soon a crop of viral myths and memes about the flu vaccine will spread over the internet.
Besides the usual BS about vaccines and autism, one specific claim that I’ve heard probably a couple dozen times in the last five years is that the H1N1 swine flu vaccines actually “killed more people than than the swine flu itself!” At least, so says quack doctor Joseph Mercola and other anti-vaccine activists.
But is it true?
The first question to answer is “how many people died from the 2009 H1N1 flu?” The World Health Organization reported about 18,500 deaths confirmed in laboratory tests worldwide. But subsequent research showed that that was a gross underestimation.
A follow up study in the journal PLOS Medicine found that: “the real toll was 10 times higher — up to 203,000 deaths. And maybe it was twice that, if you count people who died of things like heart attacks precipitated by the flu.”
Another study published a study in British medical journal The Lancet by researchers at the Centers for Disease Control put the death toll up to 15 times higher: “…The virus probably killed between 105,700 and 400,000 people around the world in its first year alone, and an additional 46,000 to 179,000 people likely died of cardiovascular complications from the virus.”
The reason for this measurement difficulty is that “flu”, while common and deadly, is actually rarely listed as the cause of death on death certificates, and few doctors, even in the West where resources exist, take the time to do laboratory tests on patients who are already dead. The number of confirmed laboratory tests thus is a very poor measure of the total number of deaths, and more advanced statistical modelling of deaths from flu-related causes is needed get an accurate measure of mortality from the flu.
The Lancet and PLOS Medicine studies give an appropriately conservative range of estimates, but it’s clear that at least some hundreds of thousands died from the swine flu and its complications: as few as 151,700 or as many as 579,000, according to CDC study. This is within the normal range for seasonal flu deaths.
So what about the number of people who died from the vaccine? This can also be hard to measure, particularly because vaccines are rigorously tested and vetted for safety before being released for public use, and flu vaccines are generally very safe for most people.
But we do have some numbers to work with. The WHO’s director of vaccine research, Dr. Marie-Paule Kieny, estimated that the vaccine “has the same safety profile as the seasonal flu vaccine,” and “there have been a similar number of events reported as we would see for seasonal flu vaccine.”
What does this mean? In November of 2009, 65 million doses had been administered, with a rate of 1 adverse reaction reported (but not necessarily confirmed) in 10,000 doses. The events are usually mild, “local reactions, such as pain at injection site, swelling, redness and reactions such as fever, headache, muscle pain, or fatigue.” Of the adverse reactions, only 1 in 20 was a severe event, giving an overall severe adverse reaction rate of 1 in 200,000 vaccinations.
After 65 million doses, only 30 deaths had been reported as being potentially linked to the vaccine–a rate of less than 0.5 per 1,000,000. Given such a large sample size, a few deaths are bound to occur after immunization, but that does not mean they are causally linked. Of the few cases that were reported, Dr. Kieny said, “results of the completed investigations reported to WHO have ruled out that the pandemic vaccine is the cause of death.”
In the United States, the Vaccine Adverse Event Reporting System–the FDA’s voluntary, unsystematic, unmoderated reporting system, where anyone can submit any report claiming whatever they want about a vaccine, such as turning your child into The Hulk–does provide some data about claimed adverse events after the H1N1 shot.
In November 2009, the CDC found that of the 46 million H1N1 vaccine doses delivered in the US, there were 3,182 adverse events reported, for a rate of about 0.7 events per 10,000 doses–not significantly different from the season flu vaccine. Of the adverse events, only 177 were severe, a rate of about 0.8 severe reactions per 200,000 doses. 11 deaths were reported–a rate of less than 0.25 per 1 million–but subsequent investigation by was unable to find any common link between the deaths that would suggest a connection to the vaccine.
In Canada, by November, 6.6 million doses had been delivered across the country, with 634 adverse reactions reported, a rate of 0.9 adverse events per 10,000 doses. Only 36 reactions were categorized as severe, a rate of about 1.1 per 200,000–less than the average for the seasonal flu vaccine. The only reported death came from an octogenarian who died of anaphylaxis, for a rate of 0.15 deaths per 1 million doses.
What does this tell us? First, there were very few severe adverse events, and even fewer deaths, alleged to be connected to the vaccine, and almost none were ever confirmed. The H1N1 vaccine was as safe and effective as the typical seasonal flu vaccine.
The WHO estimated there would be about 3 billion vaccine doses administered in 12 months. If we assume the highest reported rate of severe reactions to the vaccine–1 in 200,000–there were potentially 15,000 severe events worldwide. If we look at the highest reported (if not confirmed) rate of deaths associated with the vaccine–a little less than 1 in 2 million–there would have been fewer than 1,500 deaths from the vaccine.
The conclusion is clear: the swine flu killed between 151,000 and 579,000 people worldwide in the 2009/2010 flu season. Meanwhile, probably fewer than 1,500 people had a lethal reaction to the vaccine, which had an immunization effectiveness of 97% in adults.
While the doomsday rhetoric and media hysteria about the swine flu was, in retrospect, quite overblown, the H1N1 virus was a severe and deadly threat. There is much to criticize about the WHO and CDC’s botched responses to the pandemic–their biggest failure was in fact their inability to get enough vaccine produced and distributed before flu season started–but the H1N1 vaccine saved countless lives, with very few associated deaths and hardly any confirmed by subsequent investigations.
This season, listen to the science: get a flu shot, and spare yourself (and the immunocompromised who can’t get the vaccine) the pain and dangers of influenza.