Global Vaccine Safety

Six common misconceptions about immunization

"Vaccines cause many harmful side effects, illnesses, and even death - not to mention possible long-term effects we don't even know about."

Vaccines are actually very safe, despite implications to the contrary in many anti-vaccine publications. Most vaccine adverse events are minor and temporary, such as a sore arm or mild fever. These can often be controlled by taking paracetamol after vaccination. More serious adverse events occur rarely (on the order of one per thousands to one per millions of doses), and some are so rare that risk cannot be accurately assessed. As for vaccines causing death, again so few deaths can plausibly be attributed to vaccines that it is hard to assess the risk statistically. Each death reported to ministries of health is generally thoroughly examined to assess whether it is really related to administration of vaccine, and if so, what exactly is the cause. When, after careful investigation, an event is felt to be a genuine vaccine-related event, it is most frequently found to be a programmatic error, not related to vaccine manufacture.

Diphtheria-tetanus-pertussis (DTP) vaccine and Sudden Infant Death Syndrome (SIDS)

One myth that won't seem to go away is that DTP vaccine causes sudden infant death syndrome (SIDS). This belief came about because a moderate proportion of children who die of SIDS have recently been vaccinated with DTP; on the surface, this seems to point toward a causal connection. This logic is faulty however; you might as well say that eating bread causes car crashes, since most drivers who crash their cars could probably be shown to have eaten bread within the past 24 hours.

If you consider that most SIDS deaths occur during the age range when three shots of DTP are given, you would expect DTP shots to precede a fair number of SIDS deaths simply by chance. In fact, when a number of well-controlled studies were conducted during the 1980s, the investigators found, nearly unanimously, that the number of SIDS deaths temporally associated with DTP vaccination was within the range expected to occur by chance. In other words, the SIDS deaths would have occurred even if no vaccinations had been given.

In fact, in several of the studies, children who had recently received a DTP shot were less likely to get SIDS. The Institute of Medicine reported that "all controlled studies that have compared immunized versus non-immunized children have found either no association . . . or a decreased risk . . . of SIDS among immunized children" and concluded that "the evidence does not indicate a causal relation between [DTP] vaccine and SIDS."

Looking at risk alone is not enough however - you must always look at both risks and benefits. Even one serious adverse effect in a million doses of vaccine cannot be justified if there is no benefit from the vaccination. If there were no vaccines, there would be many more cases of disease, and along with them, more serious side effects and more deaths. For example, according to an analysis of the benefit and risk of DTP immunization, if there was no immunization program in the United States, pertussis cases could increase 71-fold and deaths due to pertussis could increase four-fold. Comparing the risk from disease with the risk from the vaccines can give us an idea of the benefits we get from vaccinating our children.

The fact is that a child is far more likely to be seriously injured by one of these diseases than by any vaccine. While any serious injury or death caused by vaccines is too many, it is also clear that the benefits of vaccination greatly outweigh the slight risk, and that many, many more injuries and deaths would occur without vaccinations. In fact, to have a medical intervention as effective as vaccination in preventing disease and not use it would be unconscionable.

WHO gratefully acknowledges the permission of CDC Atlanta, to present an edited version of "Six common misconceptions about immunization".