January 11, 2013

Many of us cannot recall the devastating effects caused by diseases like smallpox and polio. Successful vaccination programs worldwide have either eradicated these diseases or significantly limited their impact to only a few cases each year.

"Immunizations have made the largest impact on the health of our population," said Raheel Khan, MD, FAAP, a specialist in pediatric infectious diseases. "Vaccine-preventable diseases are no longer a major cause of death in children, and vaccines have played a major role in increasing the life expectancy by 30 years."

People may think that since many of these diseases haven't appeared in years, that they do not need to have their children vaccinated. "I think the public perception about vaccination has changed, in part, because people don't see these diseases anymore and don't think that they are a health risk. However, these diseases still exist and if we stop immunizing our population for these vaccine-preventable diseases, they have a potential to come back and spread like a wildfire if we have an un-immunized or under immunized population. The world has become a much smaller place with modern-day travel, and the next disease load can only be a flight away. We have an obligation as health care providers to keep our guard up and protect our population," Khan said.

Safety of vaccines

Another issue that has changed perception about vaccines is the publication of a study in the late 1990s that proposed a link between the MMR vaccine (measles, mumps and rubella) and autism spectrum disorders.

"I think the scare that happened because of this study has definitely hurt our effort to increase vaccination rates. Vaccination rates dropped, and there have been outbreaks because of that," Khan said. "The study was eventually retracted and the lead author of the original study lost his medical license because it was found that he manipulated evidence."

Several large, well-controlled and designed studies have been conducted since then, and none found any link between the MMR vaccine and autism.

Khan said that receiving vaccines on schedule is the best way to be protected from diseases like measles, mumps, rubella, pertussis and others.

"Parents sometimes choose to withhold or delay vaccinations. This can cause outbreaks and puts everyone at risk. No one is claiming that vaccines are absolutely safe, but there is nothing in life that is 100 percent safe. Vaccines, like many other medicines, can have minor side effects, but the benefits of vaccines hugely outweigh the risks," he said.

Vaccines are tested in very large, comprehensive clinical trials before marketing or public use. "The current rotavirus vaccine trial had more than 70,000 subjects; the HPV vaccine was tested in 30,000 women and the pneumococcal vaccine was tested in 30,000 children," Khan said. "We are constantly improving vaccines. The current vaccines are not the ones that our parents would have received."

There is also a system in place to report adverse events that occur after one receives a vaccine. The system is maintained by the Centers for Disease Control and the Food and Drug Administration.

Herd immunity

One of the ways in which vaccines protect against diseases is through herd immunity. "Herd immunity means that there must be a very large percentage of the population immunized in order to protect those who are not immunized," Khan said.

However, the concept is not absolute. "There are always people within a given population who have a medical reason for not being vaccinated and then there are people who do not develop immunity, even after receiving the vaccine. When people who are able to receive vaccines choose not to, the vaccination level drops below the critical percentage and puts everyone at risk," he said.

Protecting those most vulnerable

It is very important that pregnant women receive a flu vaccine to protect themselves and their unborn child. "Flu vaccines are not given to babies under six months. If a mother is vaccinated, she will transfer the immunity across the placenta to the baby," Khan said. Pregnant women should also get the Tdap vaccine to protect against tetanus, diphtheria and pertussis during the third trimester or immediately postpartum.

Also, anyone who lives with or cares for young children should receive flu and Tdap vaccines. "Babies are so vulnerable. We need to make an effort to immunize anyone who is around the baby. It's not worth taking any risks, because babies often get sicker than older children or adults and end up being hospitalized if they are infected," Khan said. "It is so important to prevent these diseases from occurring."

For more information about vaccines, visit camc.org/peds.

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