The youngest Leave the lights on blogger, my 14-month-old son, got three shots last week. He and his brother have had every vaccination recommended by pediatricians. I understand that a lot of parents are hesitant about vaccinations because of fears of their safety. Those parents should fear for the safety of their children if they don't vaccinate.

Vaccines are safe

Most of the fears about vaccinations center on the purported link between the mercury-based preservative thimerosal and autism. But study after study — most recently, one conducted in Italy — have shown that thimerosal does not cause autism. In fact, the original study that suggested the thimerosal-autism link was faked. And even if this evidence is not convincing, thimerosal is no longer used in most vaccinations.

Not vaccinating can be deadly

Last month in Minnesota, a seven-month-old baby died of Hib, or Haemophilus influenzae type b. Hib infections are vanishingly rare in the U.S. because of the routine use of the Hib vaccine, which is given at 2, 4, 6, and 12 months (this is one of the shots my son received last month). The child who died, and two of four other kids who were sickened by the Hib outbreak, were unvaccinated "because of their parents' decisions." In other words, the parents decided not to protect their children against deadly infections.

Of the other two children, one was only five months old and so had not completed the primary 3-shot series. The other had an immune deficiency. When vaccination rates are above a certain "threshold," people like these two children are protected by "herd immunity" (a term that originated in animal husbandry). The disease cannot spread because there are not enough vulnerable individuals in the population. When people choose not to be vaccinated, or not to have their children vaccinated, herd immunity suffers, and people like these two babies can be sickened.

The refusal to vaccinate one's children is a source of frustration for health officials. I cannot understand a parent's reluctance to protect their children against deadly diseases that should only be a memory in the twenty-first century.