In this day of rising health care costs it is reasonable to ask the question if mass immunization costs are worth it? It may be worth it if it only decreases the number of deaths and hospitalizations from influenza related illnesses. Some benefit appears to be from vaccinating on a community level to create herd immunity.
So what is herd immunity? Think of a group of persons in a large room. If a virus is introduced into the room it can infect the first person, multiply, infect say 3 more, multiply these 3 will infect 9 more, and so on. However if some of the persons in the room are immune to the virus then it cannot multiply in that immune individual. If more and more persons are immune in that room then it becomes very difficult for viruses to spread as it runs out of susceptible persons. If enough persons in a group are immune then the few persons with less immunity like the elderly really start to benefit from the immunity of the herd.
An estimate of this was made by Weycker et al they estimated that a 20% vaccination rate among children would decrease the number of influenza cases by 46% and an 80% coverage would be needed to decrease the disease by 91%. This is a significant finding. This can be done, as has been proven in the case of small pox where high levels of vaccination literally cornered the virus until it had no one to infect. As of december 1979 there are no human cases of small pox.
In Ontario Canada Jeffery Kwong et al did show improvement in hospitalization, emergency room visits for pneumonia and influenza like illnesses. This study was undertaken after Ontario decided to provide free influenza vaccination to all of its citizens in 2000. The study was conducted on data collected from all hospitalizations and ER visit for pneumonia and influenza like illnesses between the years 1997 and 2004. Vaccination rates increased to 38% of population from the pre 2000 rates of about 18% coverage. The data was compared to other Canadian provinces with similar population sized in the same year which had 24% vaccination coverage rates. During this time hospitalizations and deaths from influenza related illnesses decreased throughout Canada but the decrease was more pronounced in Ontario. Ontario saw 74% reduction in influenza related deaths compared with a 57% reduction in other provinces. In this study the rate of hospitalizations and ER visits was 40% less in Ontario than in other provinces. The group that saw the greatest benefit from vaccination with reference to ER visits, hospitalization and physician ER visits were the 50-64 yr age group they saw up to 80% less healthcare visits. The difference becomes much less obvious as we look at older groups that probably have other medical problems and respond less favorably to vaccination. Notably no significant increase in side effects or Guillian barre were seen in Ontario.
The societal cost savings can also be measured in terms of days lost at work, child care etc. This was shown in a study done by Bridges et al. That showed that even in years where there is a poor match between circulating virus and vaccine a net societal cost of $65.59 per person was seen in terms of lost wages compared with no vaccination. Whereas in years that a close match is seen a net societal cost of $11.17 per person is seen. These are very small prices to pay for improvement in healthcare cost.
In conclusion, there are reductions in healthcare costs with adequate vaccination though this is not seen at the individual level especially when community vaccination rates are low.