Originally posted at NeuroLogica Blog: Steven Novella addresses a study that attempts to link the H1N1 vaccine to miscarriages.
From Natural News we have more fear-mongering about the H1N1 flu vaccine, claiming:
According to the report, the rate of miscarriage among pregnant women during the 2009 H1N1 / swine flu pandemic soared by over 700 percent compared to previous years, pointing directly to the vaccine as the culprit — but the CDC denies the truth and continues to insist nobody has been harmed.
However, there was no link to “the report” – I had to do some digging to find out what this was based on, and not surprisingly I turned up a “wretched hive of anti-vaccine scum and villainy.” What I did not find was any scientific data to back up this dramatic claim.
For background, Natural News is a crank alt med site that promotes every sort of medical nonsense imaginable. If it is unscientific, antiscientific, conspiracy-mongering, or downright silly, Mike Adams appears to be all for it – whatever sells the “natural” products he hawks on his site.
So terrible is the science on this site that Adams even provoked an astronomer – Phil Plait – into writing about him. Phil makes deserved fun of Adams‘ endorsement of astrology (yes, astrology) based upon a complete butchering of a recent Nature article on seasons and circadian rhythms.
H1N1 Vaccine and Miscarriages
But back to the main story – Adams and other anti-vaccine cranks have been claiming that the H1N1 vaccine is associated with an increased risk of miscarriage (loss of a child prior to 20 weeks) and still birth (loss after 20 weeks) – collectively called spontaneous abortions. This claim is not based upon any scientific data, however.
Adams based the Natural News article (actually written by staff writer Ethan Huff) on this report by the National Coalition of Organized Women(NCOW). This article is also not a scientific report, but a press release. What were their methods?
NCOW collected the data from pregnant women (age 17-45 years) that occurred after they were administered a 2009 A-H1N1 flu vaccine. The raw data is available on the website.
Using the Vaccine Adverse Event Reporting System (VAERS), including updates through July 11, 2010 as a second ascertainment source, capture-recapture statistical methods* were used to estimate the true number of miscarriages and stillbirths following A-H1N1 flu vaccination in the U.S. Typically, even so-called “complete” studies conducted by the CDC have been shown to miss from 10% to 90% of the actual cases because of under-reporting.
Hmmm…so they combined reports from VAERS and from their own data collection. There is no indication that they controlled in any way for double counting – women who reported their miscarriage to both VAERS and NCOW.
I was also interested in their statistical methods for estimating the “true” rate of miscarriages from these reports. They indicate that cases may be underreported by “10-90%” – that’s quite a range. So someone did a fancy statistical manipulation to “estimate” the true rate based upon these two sources of reporting.
That someone is Paul G King – a notorious (in my opinion) anti-vaccine crank, who also is the NCOW science adviser. I have score of e-mail from King who likes to SPAM scientists and skeptics with crank nit-picky deconstructions of scientific or “pro-vaccine” articles. King is hardcore anti-vaccine, and is hardly an objective scientist.
His analysis amounts to a pile of assumptions used to inflate the number of apparent cases of miscarriages in women receiving the H1N1 vaccine.
I wanted to review the “raw data” that was promised in the press release, but all I could find on their website was this list of 72 anecdotal reports.
From the anecdotal reports in VAERS (219 total reports) and solicited by NCOW, how can King or anyone else conclude that any of these cases were caused by the H1N1 vaccine? In order to do that you would have to demonstrate that the number of cases exceed the background rate – an analysis which is conspicuously absent.
Fortunately, actually scientists, who understand the need to compare incidence to the background, did an analysis prior to the use of the H1N1 vaccine. Here is the entire abstract:
Because of the advent of a new influenza A H1N1 strain, many countries have begun mass immunisation programmes. Awareness of the background rates of possible adverse events will be a crucial part of assessment of possible vaccine safety concerns and will help to separate legitimate safety concerns from events that are temporally associated with but not caused by vaccination. We identified background rates of selected medical events for several countries. Rates of disease events varied by age, sex, method of ascertainment, and geography. Highly visible health conditions, such as Guillain-Barré syndrome, spontaneous abortion, or even death, will occur in coincident temporal association with novel influenza vaccination. On the basis of the reviewed data, if a cohort of 10 million individuals was vaccinated in the UK, 21.5 cases of Guillain-Barré syndrome and 5.75 cases of sudden death would be expected to occur within 6 weeks of vaccination as coincident background cases. In female vaccinees in the USA, 86.3 cases of optic neuritis per 10 million population would be expected within 6 weeks of vaccination. 397 per 1 million vaccinated pregnant women would be predicted to have a spontaneous abortion within 1 day of vaccination.
Spontaneous miscarriages are common – so common that for every 1 million vaccinated pregnant women, there would be 397 cases of miscarriage within 24 hours of receiving the vaccine, by chance alone, without any effect from the vaccine itself. (There are > 4 million births per year in the US and about 50% of pregnant women received the H1N1 vaccine last season.) This is greater than the number of cases reported through VAERS and the NCOW. But the NCOW, in their press release, assumes that all reported cases were caused by the vaccine, when there is no reason to believe that any of them were.
What is missing is a comparison of the relative risk of having a miscarriage or stillbirth in pregnant women who are vaccinated vs unvaccinated. When these analysis are done, (see abstract 871, andsee here) there does not appear to be any increased risk of any serious adverse event in vaccinated women. And further, surveillance does not reveal any increase in the background rate of spontaneous miscarriages or stillbirth following the vaccine.
In fact, let’s take another look at the numbers. There are about 4.2 million births a year in the US. About 15-20% of pregnancies result in spontaneous abortion (miscarriage or stillbirth). Even if we take the lower number, that’s 700,000 spontaneous abortions per year, or 58,000 per month. This means that over the two months of the vaccine program in 2009-2010, 116,000 women in the US would have had a spontaneous abortion. Half of them were vaccinated. Let’s further say that half of those vaccinated had their miscarriage or stillbirth after they were vaccinated – this leaves us with about 29 thousand woman who had spontaneous abortions following getting the H1N1 vaccine last season – just as the background rate.
So King’s estimates, based upon wild extrapolation from a few hundred reported cases, is still short of the background rate by an order of magnitude.
The King analysis is nothing but rank pseudoscience, twisted to his anti-vaccine agenda. It has been widely repeated by anti-vaccine, anti-government, and conspiracy-mongering sites – Natural News being just one site to uncritically parrot the false assumption that reported cases of miscarriage and stillbirth are additional cases caused by the H1N1 vaccine.
In reality there is no evidence of any increased risk of spontaneous abortion from the flu vaccine or H1N1 vaccine specifically. The CDC monitoring of reported cases has not revealed any increased risk, nor have any direct comparisons of vaccinated vs unvaccinated (with the flu vaccine) pregnant women.
And yet the NCOW accuses the CDC of lying and falsifying their reports – because they present the public with science rather than King’s pseudoscience.
Meanwhile, the H1N1 flu presents an actual risk to pregnant women and their unborn children. Fear-mongering about the vaccine, therefore, has a body toll attached to it. The NCOW does this under the guise of defending the rights of women. Mike Adams seems only to want to sell his wares. I’m not sure which is worse.