In recent years we have seen a resurgence of pertussis cases across the United States. Pertussis, also known as whooping cough, causes a lengthy coughing illness in adolescents and adults and can be life threatening to young children. This increased incidence is thought to be related to decreasing immunity over time associated with the newer “acellular” vaccine, the cyclical nature of pertussis, possible genetic changes in recent circulating strains, and decreased “herd immunity” caused by lower rates of vaccination. Herd immunity occurs when a high percentage of a population is vaccinated. A high level of vaccination within a community will decrease the likelihood of a disease outbreak and provide some protection against illness to both vaccinated and non vaccinated persons. If the immunization rate dips below “herd immunity” level the community will be at risk of disease outbreaks. Prior to introduction of the pertussis vaccine, the United States saw more than of 200,000 cases of pertussis every year. By the late 1990’s we were seeing less than 10,000 cases reported nationwide. This number crept up to 25,000 cases in 2004, and more pertussis cases were documented in 2010 than in any year since 1947!
In October, Pediatrics published an article looking at nonmedical (religious or philosophical) vaccine exemptions and clusters of pertussis outbreaks. The study evaluated rates of pertussis in schoolchildren in California from 2005-2010. The rate of nonmedical vaccination exemption tripled from 0.77% in 2000 to 2.33% in 2010. Importantly, parents who chose not to vaccinate their children often lived in close proximity to other like-minded parents and some communities had exemption rates as high as 84%. People who lived within one of these exemption clusters were 2.5 times more likely to also be in a pertussis cluster. In other words, people living in areas with high rates of non-vaccination were more likely to be affected by pertussis outbreaks.
Common Vaccine Myths
1) Choosing not to vaccinate my child does not affect anyone else – False. As the number of persons choosing not to vaccinate increases, the overall herd immunity of a community declines, placing the community at risk for an outbreak. Also, some people are not able to be vaccinated due to different health concerns (too young to receive certain vaccines, many children undergoing cancer treatments, and children with some immune problems). These children are all especially vulnerable to developing severe illness if they contract a vaccine-preventable illness and rely on herd immunity to be safe from illness.
2) My child is vaccinated so they are not at risk – False. No vaccine is 100% effective at preventing disease in all persons. The acelluar pertussis vaccine is known to have decreasing immunity and even vaccinated persons are at risk of acquiring the illness after several years. For easily spread infections such as pertussis and measles a herd immunity rate of at least 95% is necessary to prevent outbreaks and to keep the entire community safe. A very small number of vaccinated children will have poor immune response and won’t develop lasting immunity. These children also need to rely on herd immunity to stay safe from illness.
3) Vaccines cause autism – False. Numerous studies have been done looking for an association between autism and vaccines. No correlation has been found.
4) Vaccines contain mercury- False. Thimerosal, a type of mercury, used to be a common preservative used in vaccines. With the exception of some multi-vial flu vaccines it has been removed from all pediatric vaccines. Most pediatric clinics carry thimerosal- free flu vaccines as well.
5) Babies are getting too many shots too early – False. Vaccines are given early in life for a reason. Young children and babies are at especially high risk for complications from many of these illnesses. In 2008 there was a Haemophilus influenza (Hib) meningitis outbreak in Minnesota. Five children contracted the disease. One of these children died. Three were unvaccinated, one was too young to have completed the primary series, and one child had an immune deficiency. Some parents ask me about alternative vaccine schedules. This decision should not be taken lightly and should be discussed in conjunction with your pediatrician. The current vaccine schedule was designed to keep your child and our society as a whole healthy. The Institute of Medicine (IOM) recently did an in depth investigation into the current vaccine schedule. They found no safety concerns associated with the current vaccine schedule. They did, however, find increased risk of illness and outbreaks associated with delayed or modified vaccine schedules. The American Academy of Pediatrics, Institute of Medicine, and Centers for Disease Control (CDC) all advise that children be vaccinated on schedule.
6) Children’s immune systems can’t handle vaccines. – False. Children’s immune systems are designed to handle new antigen (components of vaccines and diseases) exposure. In fact, they encounter more antigens simply though every day play and exposure than from the entire primary vaccine series. Due to improvements in vaccine manufacturing, the primary vaccine series today contains fewer antigens than single vaccines used 50 years ago.
7) Natural immunity is better – False. As a pediatrician I have seen numerous cases of vaccine preventable illness. I have seen babies hooked up to breathing tubes, children die, and countless unnecessary hospitalizations and complications from illnesses that could have been prevented by following the recommended vaccine schedule. I am proud to say that my 2 year old child is fully vaccinated.
Atwell, et all. Nonmedical Vaccine Exemptions and Pertussis in California, 2010. Pediatrics. Vol 132, Num 4, Oct. 2013; 132:624-630