Dec 05 2011

Vaccine Acceptance Still an Issue

Perhaps the weak link in the effectiveness of vaccines is public acceptance. Individual vaccine types vary in terms of their effectiveness, but all are reasonably effective and very safe. Vaccines are, in my opinion, one of the “home runs” of modern medicine – scientists hit upon a way to marshal our own immune systems to make us resistant or even completely immune to certain infectious diseases. The result has been a dramatic decrease in diseases that used to plague humanity, and the complete eradication of one (smallpox).

It is ironic that the greatest barrier to the effectiveness of the vaccine program is public acceptance. Part of the problem is that very high acceptance is needed in order to achieve what is called “herd immunity” – where there is sufficient protection in the population that an infected individual will likely not cause an outbreak.

In the US the numbers are pretty good, and have remained so even through the recent increase in the anti-vaccine movement. About 68% of children complete the full routine vaccination series. Many of the individual vaccines have compliance rates in the 90s (MMR, for example, was 92.1% in 2008). The level required for herd immunity varies, but it is generally around 85-90%.

Acceptance of the flu vaccine in the US is much lower. Last year the cumulative flu vaccine use in the >6 month old population was 43%. Many people feel that the flu vaccine is not necessary, that it doesn’t work, or even that it is not safe. Uptake is slowly increasing – we  are at slightly higher levels this year compared to last year, but there is still a long way to go. The flu vaccine does have the added challenge of matching the strains covered in the vaccine to the circulating strains, so efficacy does vary from year to year, averaging about 50% effective. This year, so far, it seems that the match is a good one. We are nowhere near herd immunity levels with the flu vaccine.

Increasingly parents are opting for alternative vaccine schedule – 13% according to a recent survey.  And yet, there is no evidence that any of these alternate schedules is any safer than the standard schedule, but they are less effective – they leave children vulnerable for longer to vaccine-preventable diseases. Use of an alternate vaccine schedule, in my opinion, represents a fundamental mistrust of the medical system. The vaccine schedule is not arbitrary. It is based upon a careful review of evidence, matching the timing of each vaccine to when it is needed and when the child’s immune system is mature enough to handle it. The need for booster shots is determined by measuring antibody levels in response to vaccination. All this evidence is reviewed by panels of experts to determine the optimal schedule.

In place of this system 13% of parents would rather substitute either their own judgment or “Dr. Bob’s Alternative Vaccine Schedule.” They apparently buy into the notion that some lone maverick is better able to parse the research than panels of experts.

The historical relationship between vaccine implementation and the reduction of specific infectious diseases is very clear (which does not stop the anti-vaccinationists from denying it). Further, as pockets of vaccine denial are becoming more common, so is the recurrence of vaccine-preventable diseases. Right now Europe is in the midst of a measles outbreak, with more than 26,000 cases, 9 deaths, and 7,288 hospitalizations so far this year. MMR (measles, mumps, rubella) vaccine uptake is lower in Europe than the US. They are also dealing with many immigrant populations with lower levels of vaccine use, so it’s not all vaccine refusal.

This raises another issue with vaccine use – they are very cost effective. In case you haven’t noticed, we are in the middle of a growing health care cost crisis. The cost of health care is a complex issue I cannot get into here – but what is clear is that vaccines are extremely cost effective. In some cases they may even be cost saving – the cost of vaccine is lower than the health costs of hospitalizations they prevent.

Outbreaks of vaccine-preventable diseases are also occurring in the US. Recently there has been an outbreak of whooping cough on Long Island, for example. Whooping cough is a potentially serious illness, especially in infants. Infants are vulnerable until they are old enough to get the vaccine themselves and so depend upon herd immunity.

Often anti-vaxers point out that when such outbreaks occur it is common for most infected individuals to be among the vaccinated. They imply that vaccines therefore do not work. This is also the case with the whooping cough outbreak. This is an abuse of statistics, however.

What is important is the risk of getting the disease in the vaccinated vs unvaccinated populations. With > 90% of the population getting the vaccine the vaccinated population is much larger than the unvaccinated population. Being vaccinated greatly reduces the risk of getting the disease. Also, if someone gets the disease despite being vaccinated they are likely to have a much milder course.

It also should be noted that while overall vaccine rates are high, there are pockets of low compliance (and these are locations where outbreaks are sometimes occurring).

Anti-vaxers often cite the parents’ right to “informed consent” concerning vaccines. I agree – parents should be fully aware of the risks and benefits of vaccines. When informed with accurate information (as opposed to the misinformation from anti-vaxers) the decision to vaccinate should be an easy one.

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