The defeat of smallpox illustrates the value of vaccination. That terrible disease had a mortality rate of 30 percent and over the course of human history killed 300,000,000 people. The last case occurred in 1977 after a prolonged vaccination campaign. No one will ever get smallpox again.

We can hope to abolish other diseases if enough people accept vaccination. Polio and measles are next on the list.

In the U.S., the number of cases of 10 vaccine preventable diseases dropped from 1,113,009 a year before vaccines to 11,539 in 2007.

Vaccines are the greatest achievement of modern medicine, but some people have come to distrust them and are refusing vaccinations. What’s going on?

In 1998 Andrew Wakefield published a study suggesting that the Measles-Mumps-Rubella (MMR) vaccine might cause autism. The study was later retracted, Wakefield was found guilty of misconduct and follow-up studies showed there was no link between MMR and autism; but worried parents let the MMR vaccination rate drop in the UK to as low as 50 percent in some areas. Measles became endemic again. Children died.

In the U.S., the mercury-containing preservative thimerosal was accused of causing autism. Studies showed no link, and the rate of autism didn’t drop when thimerosal was removed from vaccines. Some people like Jenny McCarthy are still blaming vaccines for autism despite the lack of evidence.

Some protest that it’s against nature to inject antigens into the human body. But if nature is trying kill you, isn’t going against nature a good thing?

Some fear other ingredients in the vaccines, such as formaldehyde, ether, squalene, anti-freeze and aborted fetal tissue. Some of these were used in manufacture but are not present in the final product, some never were in the vaccines, and others are present in tiny amounts that are known to be harmless.

Sometimes vaccines cause adverse effects. But the vaccines are far safer than the diseases. Measles causes pneumonia in 6 percent, encephalitis in 0.1 percent and death in 0.2 percent. The measles vaccine causes encephalitis or severe allergic reaction in 0.0001 percent.

Some fear that vaccines overwhelm babies’ immune system with too many antigens. But babies already handle the thousands of antigens they encounter in their environment every day, and adding a few more antigens from vaccines is negligible.

Some accept vaccination but only on a delayed schedule. There is no scientific rationale for delaying them, and babies remain susceptible to catching the disease until they get the vaccine.

Some say since there is currently no polio in the U.S., they don’t need to be vaccinated. But all it would take is one person with polio on an airplane and we could have an epidemic.

Some depend on herd immunity. If enough people in a community are immune, the disease won’t be able to spread. You can selfishly refuse to get your shots and let your neighbors take any possible risks from the vaccine and ride to safety on their coat-tails. If everyone did that, herd immunity would vanish.

If a disease is introduced into a community, the unvaccinated are far more likely to get sick, but the vaccinated are at risk too because vaccines are not 100 percent effective. By not getting vaccinated, you are endangering everyone’s public health.

In some areas of the U.S., the vaccination rate is far below the rate needed to ensure herd immunity. According to CDC data, Washington state still has an immunization rate 73.5 percent lower than the national average 76.1 percent.

Small outbreaks of vaccine-preventable diseases have already occurred and we can expect more unless the vaccination rates rise. By one estimate, 500 people have died from vaccine-preventable deaths in the U.S. in the past 2½ years.

They didn’t need to die.

Harriet Hall retired as a full colonel from the Air Force officer after 20 years as a flight surgeon.