Health & Social Policy

Freeriding on Herd Immunity

Recently, the Republic of Congo reported more than 150 deaths from polio, as well as more than 200 cases of paralysis due to polio. This comes as a shock to members of developed countries in which polio remains just a story of older generations. To the progressively more vaccine-averse generations of the United States, polio is just a non-threatening word – but it means so much more than that.

Although polio produces minor symptoms or no symptoms at all in 95 percent of cases, the disease does produce temporary or permanent paralysis in 5 percent of those infected. This is significant when considering that at its height in the United States in 1952, 57,628 cases were reported. The disease also targets children, especially those under five years of age, making it more startling than other diseases with more severe or prevalent symptoms.

And yet, in states that allow personal exemptions from the mandatory immunizations for children, there is a growing group of objectors who do not wish to vaccinate their children for polio or other diseases. This group is still small – only 20 states allow personal exemptions, although all states offer medical exemptions. In 2004, only 2.54 percent of children in those 20 states were not immunized. As a result, herd immunity created by overall adherence to immunization requirements still protects these children from disease. Growth of dissention could change that.

The New York Times reported that those claiming exemptions were tending to clump in certain geographic areas, making outbreaks more likely to occur. Some communities had an exemption rate as high as 10 to 18 percent, putting children in those areas in danger.

And these outbreaks are already occurring. A 2008 measles outbreak in San Diego affected 12 children, while a 2005 outbreak affected 34 people; a 2006 mumps outbreak in Iowa affected 219 people; and in 2005, there was a polio outbreak in Minnesota affecting children in an Amish community, who refrain from vaccination for religious reasons.

Abstaining from the polio vaccine does not just affect one child, and if exemptions become widespread enough, it can even affect other regions and countries. In 2003, the state of Kano in Nigeria boycotted the vaccine for a year, and ended up exporting polio cases to 12 neighboring countries that had recently eradicated the disease. The World Health Organization states that in 2009 to 2010 alone, “23 previously polio-free countries were re-infected due to imports of the virus.”

Exemption policy for immunizations may be an important part of U.S. policy, since several religious groups object strongly to vaccines for one reason or another. However, The New York Times states that in some states, obtaining an exemption is easy, requiring little paperwork, which encourages parents to act on uncertain or unproven information concerning vaccines’ safety.

If making vaccinations mandatory across the board is not an option, procedures for securing an exemption should be made more rigorous and involved, to discourage parents without serious objections to the vaccine from pursuing exemptions, or at least to encourage greater research and thought into the concept of vaccinations. Efforts should also be made to educate the American public on the real facts of the diseases targeted by vaccinations and any side effects of immunization.

We cannot continue to depend on herd immunity to keep outbreaks from growing in intensity without encouraging as many people as possible to join the ranks of the vaccinated. We must increase public knowledge about the science behind the immunization process as well as its importance.

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