Charlotte A. Moser, Assistant Director, Vaccine Education Center at The Children’s Hospital of Philadelphia
Originally published in September 2011 Parents PACK newsletter
I can’t believe that summer is over already! Our family had a great summer, but it was really busy as we travelled with my teenage son and his baseball team. We were so excited in the spring when he was invited to participate on this team of mostly older boys, and he was over the moon as he heard about trips planned for up and down the east coast. As a family, we decided that at least one parent would accompany him on every trip, but that whenever we could, the whole family would go. My husband and I worked out the schedule in a way that we were both in and out of the office throughout this intense period of travel.
For me, being in the office meant monitoring information about disease reports. It meant learning about the measles outbreaks that were occurring in multiple states, hearing about cases of whooping cough that were continuing to be diagnosed, and receiving maps detailing weekly cases of influenza. When I wasn’t at work, I was driving from state to state, sometimes with multiple teenagers in the car, seeing opposing teams and their families from many other places, and watching typical team socialization, like sleeping in cabins, eating together and — cringe! — occasionally sharing water bottles. What about those “good game” lines after every match-up? How about all the restaurants we found ourselves eating in? Of course, we had our daughter with us, so what about all those tourist attractions, movies and malls along the way?
As a mom, I wanted my son to have a great time, but I also wanted everyone to be healthy. I knew these diseases were occurring in states we were visiting, in states other teams had come from, and even in our own county. Were boys from other teams well enough to play, but sick a few days later? What about the player who was too sick to come to the start of one tournament, only to show up and stay in the cabin two days later? Were parents or younger siblings who “just didn’t feel quite right” sharing the bleachers? What about that cashier coughing while she rang up our snacks for the team?
My family was up to date on our immunizations, but I also knew that was not a guarantee. A vaccine might not work for any number of reasons, and I knew there were not vaccines for every type of virus or bacteria that could cause an illness. But, I did take comfort in the fact that I had done what I could to protect my family. Measles vaccine? Got it. Influenza vaccine? Yes. Pertussis vaccine? You bet.
Now that I am back in the office, I have looked over the disease reports for that period a bit more closely. I saw reports of Haemophilus influenzae type b, meningococcal disease, hepatitis B, pneumococcus, chickenpox, hepatitis A and mumps. The reports were from states we had visited or from states that other teams called home. Were we exposed? Maybe. Maybe not. None of us got sick, so I’d like to think we weren’t, but we really don’t know. The vaccines may just have been doing their job.
Now school’s back in session. We should be good, right? Did I mention the email I just got that says about half the kids in my son’s school don’t have complete immunization records? I sit here hoping it is just the records and not the vaccines that are missing. And then I go through the mental list: Measles vaccine? Got it. Influenza vaccine? Yes. Pertussis vaccine? You bet.
One of the contested concepts in vaccines these days is the idea of immunizing one’s children to protect others. People fearful about the safety of vaccines feel they may be risking the health of their children for someone else’s benefit. So, exactly what is herd immunity?
Herd immunity is the finding that if enough people in a community are immunized, even those living among them who have not been immunized are less likely to get a disease. Herd immunity is really a numbers game: the more people that are protected from the disease, the lower the number of susceptible hosts; therefore, the less virus or bacteria moving throughout the community. In fact, a study done by Susan Van den Hoff and colleagues in The Netherlands published in 2002 found that unimmunized people in a highly immunized community are better protected against measles than immunized people in a community with lower immunization rates.
The ability to protect community members (the “herd”) in this way depends upon a few things:
Because immunization rates in the U.S. have been high for many vaccines such as measles, mumps, rubella, Haemophilus influenzae type b (Hib), and polio among others, our communities have enjoyed herd immunity. Most of us have not seen these diseases in recent years. In fact, in many of our communities, this still holds true. Unfortunately, however, recent concerns about the safety of vaccines in certain communities have created pockets of susceptible people throughout the country.
We all understand that when we are around someone who is sick, we may get sick too. Most of us also realize that vaccines help decrease the spread of some diseases. However, the notion that the vaccines we receive can help protect those around us is sometimes more difficult to understand.
Researchers at Dartmouth have developed a board game, known as the POX game, to help players gain a better understanding of how the number of immunized people in a community, as well as the presence of people who are immune compromised, plays a role in how quickly diseases can spread throughout a community. The group is developing an online version of the game as well. To learn more about the game, go to http://www.tiltfactor.org/pox.
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