A May 20 Instagram post (direct link, archive link) shows a screenshot of a tweet that tries to link routine childhood immunizations and sudden infant death syndrome.
"I just heard from a reliable source that 98% of SIDS deaths happen within 10 days of vaccination," reads the tweet. "It's a good thing we don't make this public health data public, isn't it? Otherwise, we'd learn the truth. Also, in Japan, they pushed back the vax schedule by 2 years and SIDS disappeared."
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The post was liked more than 400 times in a month. The original tweet was retweeted more than 6,000 times in a month.
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Routine immunizations do not make infants more likely to die from SIDS, experts say, and the shots may actually decrease the likelihood of sudden infant death. Multiple experts agreed there is no evidence SIDS has disappeared in Japan.
The tweet by technology entrepreneur Steve Kirsch makes two claims about the supposed risks of recommended childhood vaccines. Kirsch, who frequently shares vaccine misinformation, acknowledged in the post that he has no data to back up his claims, asking followers, "Does anyone have the reference to either of these?"
Experts say the evidence points to there being no causal link between vaccinations and SIDS. A metanalysis of studies found the rate of SIDS could be halved by vaccination. The authors said vaccines, at a minimum, do not cause SIDS.
"Vaccines have been looked at a number of times and there has been no association shown," said Dr. Sean O'Leary, director of the Colorado Pediatric Practice-Based Research Network for Children's Hospital Colorado.
O'Leary said risk factors for SIDS include placing a child to sleep on its back, loose bedding, maternal drinking and smoking around an infant.
Dr. Paul Offit, director of the Vaccine Education Center at Children's Hospital of Philadelphia, said the vaccination schedule is active when children are 4 to 6 months old, but most SIDS cases happen before children are 6 months old regardless of their vaccination status.
Kirsch, in a Substack post he mentioned in a reply to the tweet, pointed to data from the Vaccine Adverse Event Reporting System he claimed illustrated a causal link between vaccinations and SIDS. Offit noted that VAERS reports are unverified, anecdotal claims that anyone can make, so they cannot be used to prove causation.
The database's website says anyone can submit a report, including the general public, and it has a disclaimer that states, "VAERS reports may contain information that is incomplete, inaccurate, coincidental or unverifiable. Reports to VAERS can also be biased. As a result, there are limitations on how the data can be used scientifically."
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Offit, O'Leary and Dr. Fern Hauck, director of the International Family Medicine Clinic at the University of Virginia Health System, each looked at the recommended vaccination schedule published by the Japan Pediatric Society and agreed it did not vary significantly from the U.S. schedule. None could find any evidence that Japan pushed back vaccinations or had eliminated SIDS, as the post claims.
One issue that makes comparing SIDS rates difficult is the inconsistency in how deaths are tracked between - or even within - countries, the doctors agreed. A 2015 study highlighted the variance, noting there are three International Classification of Diseases-10 codes that could be used to track sudden, unexplained deaths of infants, and their use varied by country. For example, 32.6% of such deaths between 2002 and 2010 in Japan were coded as SIDS (R95), which Hauk said makes the number of reported SIDS deaths seem substantially lower. But Japan was the only country that regularly uses the code for sudden unexplained infant deaths with unknown causes (R96), attaching it to 44.8% of such deaths.
When all the codes that could be used for SIDS are added together, the rates for the U.S. and Japan are much closer, Hauck said.
"There's no specific guidance on how you assign those codes, even within the U.S., so different doctors and different countries interpret the codes differently or choose to use the codes differently," said Hauck, who added that efforts are being made to revise and standardize the definitions behind the codes.
USA TODAY reached out to Kirsch and the social media user who shared the post for comment but did not immediately receive responses.
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This article originally appeared on USA TODAY: Routine infant vaccines may reduce likelihood of SIDS; they don't increase it | Fact check