Dec 14 2010

H1N1 Vaccine and Miscarriages – More Fear Mongering

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, and see 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.

11 responses so far

11 Responses to “H1N1 Vaccine and Miscarriages – More Fear Mongering”

  1. Todd W.on 14 Dec 2010 at 12:44 pm

    Any time I see VAERS mentioned in an article bashing vaccines, I can be relatively certain that the authors did not heed this tidbit from the VAERS web site:

    VAERS Does Not Determine Causality

    Although VAERS can rarely provide definitive evidence of causal associations between vaccines and particular risks, its unique role as a national spontaneous reporting system enables the early detection of signals that can then be more rigorously investigated. VAERS receives reports of many events that occur after immunization. Some of these events may occur coincidentally following vaccination, while others may truly be caused by vaccination. Studies help determine if there is more than a temporal (time) association between immunization and adverse events. The fact that an adverse event occurred following immunization is not conclusive evidence that the event was caused by a vaccine. Factors such as medical history, diagnostic tests, and other medication given near the time of vaccination must be examined to help to determine the cause of adverse events.

    DHHS really needs to make use of VAERS data conditional, that all studies based on VAERS must have the disclaimer that VAERS data may not be causally related to the vaccine reported. I’m willing to bet that King and NCOW did not investigate any of the VAERS reports to find out which ones were causal and which were merely coincidental.

    Nicely written, Dr. Novella.

  2. B Hitton 14 Dec 2010 at 12:45 pm

    Steve, what kind of profile does NCOW have outside of their anti-vax, anti-GMO echo chamber? While their arguments are clearly laughable and don’t stand up to scrutiny (your analysis here handily embarrasses them), it’s not so easy for the typical pregnant woman to see through them and their propaganda might be quite compelling.

    I’m thinking of groups like Age of Autism, which is equally ludicrous and pseudoscientific, but gets a good deal of traction in the community of frustrated parents of autistic children. Should we be as concerned about NCOW?

    Here’s an example of “data collection” NCOW-style:

  3. Enzoon 14 Dec 2010 at 1:45 pm

    Great deconstruction of a ridiculous argument. It really is sad that on such an important issue, many readers would simply trust the “report” without looking into it.

    As you’ve shown, a little bit of information about the numbers and some napkin math reveals the truth. A shame more people don’t take this approach to any report they read. I hope this doesn’t get picked up by mainstream media.

  4. daedalus2uon 14 Dec 2010 at 3:25 pm

    About 5% of the deaths due to H1N1 were in pregnant women. If there are 4 million births, that means ~3 million pregnant women at any time during the year (~3 million/300 million =1%), which means ~5x more deaths among pregnant women than among the non-pregnant.

  5. VRAlbanyon 14 Dec 2010 at 9:52 pm

    Ooh! I see!
    This is a great illustration of the plural of anecdote = anecdotes/confirmation bias concept we were talking about earlier. How is a study based on a “data” set from a couple of “tell us your horrible vaccine stories” sites NOT going to be biased? I mean, they are actively stockpiling the anecdotes they want to hear. It’s almost too easy to discredit this claim, and it’s a shame that anyone would believe Adams.

    But I preach to the choir here… at least I feel like I’m getting better at this critical review thing.

    Beautiful breakdown of the numbers. Thanks for sharing.

  6. tmac57on 15 Dec 2010 at 9:35 am

    It is really distressing to read the collection of anecdotes on the anti-vax sites.Clearly the people there believe the connection between the vaccine and spontaneous abortion,and it is compelling to read account after account of “My pregnancy was going just fine,and then I had the flu vaccine,and the next day/week/month,I lost my baby”.The emotional impact of these stories are hard to counteract with charts and cold statistics.
    I was wondering if there is a statistically significant rate of spontaneous abortion among the women who contract the flu. If there is,that might be an important factor in encouraging pregnant women to get the vaccine.

  7. Calli Arcaleon 15 Dec 2010 at 10:11 am

    tmac57 — there is a statistically significant rate of *death* among pregnant women who contract the flu (and maternal death is, of course, fatal to the fetus as well). If that doesn’t persuade women to get the flu shot, I doubt miscarriage rates will.

    That said, I have read (don’t remember where at the moment, and I have only a brief moment before my compile finishes and I have to get back to work) that an increased miscarriage rate has indeed been observed in women who contracted influenza. This is not really surprising; serious illness in general is associated with an increased miscarriage risk.

    I did find this link. It discusses seasonal flu specifically, and mentions that influenza is known to cross the placental barrier.

    The big problem, of course, is that miscarriage rates are messy data. Not all miscarriages are reported, especially very early ones (which even the mother herself may mistake for a heavy period, if she didn’t yet realize that she was pregnant, especially if she has irregular periods), and concomitant factors such as influenza aren’t always reported either. Most significantly, miscarriage is far more common than most people are prepared to admit — possibly as high as a fifth of all recognized pregnancies end in miscarriage.

  8. daedalus2uon 15 Dec 2010 at 10:06 pm

    Flu is not benign to the fetus even if the fetus survives to term. I heard a talk by someone specializing in the effects of maternal illness on their fetus in utero and the statement was made that if exposure to flu in utero could be completely prevented, that the incidence of schizophrenia would go down by 20%.

  9. Science Momon 16 Dec 2010 at 1:57 pm

    I believe another crank that assisted with this VAERS dumpster-diving expedition worth mentioning is Gary Goldman. He is a fave and editor in chief for Medical Veritas. Thank you Dr. Novella for putting this rubbish into perspective.

  10. gregladenon 19 Dec 2010 at 10:59 am

    Question: Have you seen “capture and release” statistical methods used in this context before? I love innovation in statistics, but this may be a case of trying all the methods out to get a desirable result or, more likely, trying to blind the reader.

    Comment: If I read the ‘literature’ regarding miscarriage caused by H1N1 (the fake woo woo literature, not the real literature) correctly, I think they have used an “innovative” correction to make a very large estimate for the most recent year and compared it to prior years data (two years, IIRC) that were not derived using the same method. That would be way wrong.

    Also, even if their original data (that they collected) was somehow valid, I would think that this particular approach to extrapolation would be very inaccurate … or, more exactly, inaccuracies would be potentially amplified a great deal.

    Epidemiologists estimate things like flu death by interpolating from a set of symptoms often linked to flu. As a result, any over-estimate is less than the original seed numbers. That can give results that are wrong, but not too wrong. The method used in these H1N1 miscarriage studies do the opposite: They go from (allegedly) well defined cases in a very small sample to extrapolate outwards. Very bad technique.

    As far as we know, the science shows at this point that the H1N1 2009/10 flu was, as originally feared, very bad for pregnant women and their fetus. This makes this particular bit of anti-vax distortion and fear mongering especially bad.

  11. sheldon101on 30 Dec 2010 at 1:10 am

    Actually I calculated the number of miscarriages they should have reported if NCOW had done its work properly.

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