Is SIDS linked to vaccinations?

[nicole]

Date: March 12, 2003

SIDS Not Linked to Number and Variety of Childhood Vaccines

WASHINGTON -- The evidence does not support a causal link between sudden infant death syndrome (SIDS) and either the diphtheria, tetanus, and whole-cell pertussis (DTwP) vaccine or exposure to multiple childhood vaccines, says a new report from the Institute of Medicine of the National Academies. Only an older version of a vaccine against diphtheria and pertussis that is no longer administered to infants is causally related to fatal anaphylaxis, a rare and severe inflammatory reaction. These and other findings about childhood vaccines, SIDS, and other types of sudden unexpected death in infancy (SUDI) do not warrant a review of the childhood vaccination schedule, the report concluded.

"Although the timing of infant vaccinations coincides with the period when SIDS is most likely to occur, parents should rest assured that the number and variety of childhood vaccines do not cause SIDS," said Marie McCormick, chair of the committee that wrote the report and professor and chair, department of maternal and child health, Harvard School of Public Health, Boston. "We do not have the data that would definitively answer all questions about links between vaccines and SIDS and other forms of sudden, unexpected death in infancy. However, we believe that the data we do have, along with the increasing rarity of these kinds of infant deaths, make a review of the vaccine schedule unnecessary."

American children routinely receive five vaccines against seven infectious agents before age 1: the DTaP vaccine -- which contains a different form of the pertussis component than DTwP, which it replaced in the United States in 1997 -- and vaccines against Haemophilus influenzae type b, hepatitis B (HepB), polio, and pneumococcal bacteria. Although HepB is given to newborns, the others typically are administered at 2 months of age, with additional doses of certain vaccines given at 4 and 6 months.

SUDI encompasses sudden, unexpected deaths in which there may or may not be a clear cause of death. SIDS is the diagnosis most often given for infant deaths that occur without warning and for which no cause is identified. Medical researchers have not reached consensus on the risk factors for SIDS or how it occurs, although current guidelines to place babies on their backs or sides to sleep are based on theories that the prone position may contribute to SIDS. Another possible explanation, the "triple-risk" hypothesis, postulates that SIDS may occur through the interaction of an underlying biological vulnerability, a critical development period, and exposure to an outside trigger. It has been speculated that vaccination may act as such a trigger. Further research could show that there are many causes of SIDS.

Evidence from studies based on human exposure is strong enough to favor rejection of any causal connection between SIDS and multiple doses of different vaccines. In addition, the report reaffirmed previous findings that SIDS is not linked to the older DTwP. Because the currently used DTaP vaccine has fewer side effects than DTwP, the committee found no reason to suspect any link between DTaP and SIDS. However, without sufficient or adequate evidence available, the committee could not definitively reject a link between DTaP and SIDS. Evidence was also insufficient or inadequate to determine whether relationships exist between other individual vaccines and SIDS.

Although some research suggests that an abnormal immune response to common respiratory bacteria or viruses may be a factor in SIDS, there are no studies demonstrating the ability of vaccines to provoke abnormal inflammatory responses of the kinds seen in some SIDS cases. The committee concluded that the ability of vaccines to act as triggers of SIDS is only theoretical. A similar conjecture that fever or other common side effects of vaccination could spur an acute metabolic reaction in babies with an innate metabolic condition is also theoretical.

Although very rare, anaphylaxis from any cause -- such as a food, drug, or environmental allergen -- can lead to sudden, unexpected death. On the basis of a well-documented case of fatal anaphylactic shock in twin babies that occurred after each received a second dose of diphtheria toxoid and whole-cell pertussis vaccine (DwP), the committee concluded that the evidence favors acceptance of a link between this vaccine and infant death due to anaphylaxis. The case occurred in 1946, however, and the committee did not find any other well-documented reports of infant deaths related to anaphylaxis following vaccination, despite the widespread use of childhood vaccines during the 57 years since that case. Moreover, DwP is no longer used in the United States.

While the number and variety of vaccines infants receive is not linked to SIDS, there is not enough evidence to determine whether exposure to multiple different vaccines is causally linked to SUDI in general. Evidence also is not sufficient or adequate to determine if HepB, the only vaccine given to newborns, is linked to neonatal deaths, the report says.

A standard definition of SUDI should be developed, and criteria related to SIDS and SUDI should be consistently applied for research and reporting purposes. Comprehensive postmortem work-ups should be performed on all infants who die suddenly and unexpectedly, the report says.

The number of infant deaths declined between 1990 and 2000, dropping from 9.2 deaths per 1,000 live births to 6.9 per 1,000, the lowest infant mortality rate ever recorded in the United States. Because SUDI are difficult to define, there are no data on the national rate of SUDI in the United States. SIDS is the leading diagnosis for postneonatal death -- death occurring after the first 27 days -- and there were 2,523 deaths attributed to SIDS in the United States in 2000. The rate of SIDS has been declining over the past several years.

This study is the sixth in a series of eight on vaccine safety sponsored by the Centers for Disease Control and Prevention and the National Institute of Allergy and Infectious Diseases. The Institute of Medicine is a private, nonprofit institution that provides health policy advice under a congressional charter granted to the National Academy of Sciences. A committee roster follows.

Copies of Immunization Safety Review: Vaccinations and Sudden Unexpected Death in Infancy will be available later this year from the National Academies Press; tel. [phone] or 1-800-624-6242 or on the Internet at www.nap.edu. Reporters may obtain a pre-publication copy from the Office of News and Public Information (contacts listed above).

INSTITUTE OF MEDICINE
Board on Health Promotion and Disease Prevention

www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=10649

Read the study.

Download the summary as a pdf file.

[nicole]

Sudden Infant Death Syndrome (SIDS) and Vaccines

From 2 to 4 months old, babies begin their primary course of vaccinations. This is also the peak age for sudden infant death syndrome (SIDS). The timing of these two events has led some people to believe they might be related. However, studies have concluded that vaccinations are not a risk factor for SIDS.

With babies receiving multiple doses of vaccines during their first year of life and SIDS being the leading cause of death in babies between one month and one year of age, CDC has led research studies to look for possible linkages. Results from studies below and continued monitoring reassure us about the safety of vaccines.

* The Institute of Medicine (IOM) released a report on Immunization Safety Review: Vaccination and Sudden Unexpected Death in Infancy in 2003. The committee reviewed epidemiologic evidence focusing on SIDS, all sudden unexpected death in infancy, and neonatal death (infant death, whether sudden or not, during the first 4 weeks of life). The committee also looked for possible relationships between SIDS and the individual vaccines diphtheria-tetanus-whole-cell pertussis (DTwP), DTaP, HepB, Hib, and polio; and specific combinations of vaccines or any combination of vaccines. The committee did not find enough evidence to show vaccines cause SIDS.


* A study using Vaccine Safety Datalink (VSD) data, which included children who were covered by a managed care organization health plan, found no association between immunization and deaths in young children. The study investigated deaths in children one month to 7 years of age between 1991 and 1995. Data were analyzed by comparing vaccination histories for each vaccine during the week and month prior to the date of death for each child. Five hundred and seventeen deaths occurred between 1991–1995, most (59%) during the first year of life. Of these deaths, the results did not show an association between immunizations and childhood deaths.


* Studies that looked at the age distribution and seasonality of deaths reported to the Vaccine Adverse Event Reporting System (VAERS) SIDS and VAERS reports following DTP vaccination, and SIDS and VAERS reports following hepatitis B vaccination found no association between SIDS and vaccination.


* VAERS also monitors the safety of vaccines. Through VAERS the U.S. Food and Drug Administration carefully investigates all deaths following vaccination that are reported to VAERS.

As a result of the American Academy of Pediatrics' 1992 recommendation to place healthy babies on their backs to sleep, and the success of the National Institute of Child Health and Human Development's national Back to Sleep campaign, fewer SIDS deaths are reported. According to "Targeting SIDS: A Strategic Plan":

* Between 1992 and 1998, the proportion of infants placed to sleep on their stomachs declined from about 70 percent to about 17 percent.


* Between 1992 and 1998, the SIDS rate declined by about 40 percent, from 1.2 per 1,000 live births to 0.72 per 1,000 live births.

These results tell us that most SIDS deaths are due to factors like sleeping on their stomachs, cigarette smoke exposure, and mild respiratory infections.

www.cdc.gov/vaccinesafety/concerns/sids_faq.htm

RELATED LINKS:
SIDS
National SIDS/ID Resource Center*
National Center for Immunization and Respiratory Diseases
VAERS (FDA)