Based on my previous discussion on vaccines and their potential risks vs benefits, two studies are suggested to provide better insight into vaccine impact.
The following is a very basic overview of research projects that would provide a lot of information on how to maximize the overall effectiveness of vaccinations. What could impact this? Based on initial investigations, vaccines could potentially be less effective on preventing outbreaks due primarily to psychological shifts caused by poor education on the topic of vaccinations and lack of knowledge of the base effectiveness of a vaccine at preventing infection. In addition, partially effective vaccines pose the risk of creating additional diagnosed carriers for the infection. Therefore we need to study how vaccinations impact risk aversion and whether or not certain vaccines result in partial immunity allowing an individual to become infected without showing the usual symptoms.
One of the potential risks I addressed in my previous article was the possibility of decreased risk aversion due to the perception that vaccines protect us in situations where we are likely to come into contact with a diseased individual. There is currently little information available on how getting vaccinated changes the patterns of behavior of the individual. Knowing this is key to ensuring that vaccines the end results of vaccination are as effective as possible.
This study seems like the more difficult one. Simply asking if a person feels safer being vaccinated doesn’t really tell us whether or not the person is more likely to surround himself with people who are sick. It could also include a theoretical component addressing the impact fluctuations in risk aversion have on infection rates and how that impact compares to effectiveness of a vaccine on preventing an individual infection.
Work has been conducted which indicates the current pertussis vaccine may provide only partial immunity in some individuals and thus result in carriers who are not diagnosed. This is most concerning in that a person may be infected while thinking that they are disease free and thus may be more willing to come into contact with someone who has not been vaccinated. The greatest at risk group in this case would be those who are around young children. There seems to be even less information regarding the possibility of partial immunity caused by other vaccines.
This test should be easier although it might be expensive. The first step is to select which diseases we would like to identify. We would then need to find a large enough sample of individuals with detailed vaccination histories for the diseases in question. Then it’s just a matter of testing them to see if they have the antibodies suggesting that they are or have recently been infected with the illness. An issue with studying all of these diseases together is that the pool of individuals who have documentation for all of their vaccines will be much smaller.
Probably one of the best options is to look at B. pertussis (and possibly parapertussis, which also causes whooping cough) specifically and perform a longitudinal study consisting of school aged children (7 – 15). A similar, but pooled cross-sectional study was conducted in China. The study used by the culture test and PCR testing. The former tends to have a weak ability of correctly identifying infection while the latter tends to produce false positives, partially because it can pick up the DNA from recent vaccinations. This can be reduced if proper care is taken.
Only children who initially test PCR negative will be included in the study. From that point on, the number of symptomatic cases, culture positive cases, and PCR positive cases will be recorded at multiple times throughout the study. Any child who has symptoms preceeding a test and tests positive by either culture or PCR will be counted separately. How many tests and the time between testing will depend on factors such as cost and probability that children will be willing to complete the entire study. Should someone who is counted as positive at any point during the study be eliminated from the next round of tests?
Regarding the question of time between testing, PCR tests are positive for 14 – 21 days after onset of symptoms and symptoms take about 7 – 14 days to manifest. Therefore any interval longer than 21 days could miss an infection.
An alternative to the full longitudinal test is to first conduct a pooled cross-sectional study as was done in China to at least get an estimate on the total proportion of asymptomatic carriers.