Vaccine efficacy – Pneumococcal
Are vaccines effective? That is another question that worried parents often ask. Do we know for sure that these vaccines do what they are supposed to do? Well, as I’ve said before, that question is very broad, so we will try to break it down into manageable bits. This entry will look and see if we can find any evidence for the efficacy of the pneumococcal vaccine in preventing pneumonia and pneumonia deaths. As usual, PubMed makes for an excellent start. A quick search there brings up this interesting study.
Efficacy of 23-valent pneumococcal vaccine in preventing pneumonia and improving survival in nursing home residents: double blind, randomised and placebo controlled trial. Maruyama T, Taguchi O, Niederman MS, Morser J, Kobayashi H, Kobayashi T, D’Alessandro-Gabazza C, Nakayama S, Nishikubo K, Noguchi T, Takei Y, Gabazza EC. Department of Pulmonary and Critical Care Medicine, Mie University Graduate School of Medicine, Tsu City, Mie Prefecture, Japan. BMJ. 2010 Mar 8;340:c1004. doi: 10.1136/bmj.c1004.
Study Summary – The study was set up to examine the efficacy of the pneumococcal vaccine in preventing pneumonia and/or reducing pneumonia-related deaths. There were a total of 1006 participants from nursing homes in Japan. They were randomly split into two virtually equal groups (in size); one group received the vaccine, the other a placebo. The study was double-blind, meaning that non only did the participants not know if they were on the vaccine or placebo, but those administering the doses did not know either. The results showed a 39.32% decrease in all-cause pneumonia infections between the placebo and the vaccinated group (form 20.6% in the placebo group to 12.5% in the vaccine group). As far as pneumococcal pneumonia rates were concerned, it also showed a decrease, this time of 61.64%. Furthermore, no deaths occurred amongst those in the vaccinated group that developed pneumococcal pneumonia, whereas the placebo group had a death rate of 35.1%. However, death rate from ALL CAUSE pneumonia did not differ between the two groups. The study’s conclusion was as such:
CONCLUSION: The 23-valent pneumococcal polysaccharide vaccine prevented pneumococcal pneumonia and reduced mortality from pneumococcal pneumonia in nursing home residents
So how should we interpret this study? I interpret it like this: the pneumococcal vaccine was significantly effective (as compared to placebo) in preventing both infections and deaths by pneumococcal pneumonia. The vaccine appears to be highly effective for the age group the study investigated. It also significantly decreases all-cause pneumonia infections, but appears to have no effect in death rates for all-cause pneumonia.