Rotaviruses are one of the most common causes of gastroenteritis in children.  A new rotavirus vaccine was introduced a few years ago; what impact has it had on disease?

This study confirms on a national scale that the 2008 rotavirus season among children aged <5 years was dramatically reduced compared to pre-RV5 seasons.  …  Based on the observed decrease during the 2008 season, we estimated that ~55,000 acute gastroenteritis hospitalizations were prevented during the 2008 rotavirus season in the United States. A decrease of this magnitude would translate into the elimination of 1 in every 20 hospitalizations among US children aged <5 years.1

(My emphasis)

Here’s what that looks like:

Rotavirus vaccine vs. gastroenteritis

Monthly acute gastroenteritis and rotavirus-confirmed hospitalization rates.  The rotavirus vaccine was introduced in 2006; in 2007 about 3% of children were completely vaccinated; in 2008 about 33% were vaccinated 1

Interestingly, the reduction in gastroenteritis wasn’t only in vaccinated children:

In 2008, acute gastroenteritis hospitalization rates decreased for all children aged <5 years, including those who were either too young or too old to be eligible for RV5 vaccination. …These findings … raise the possibility that vaccination of a proportion of the population could be conferring indirect benefits (ie, herd immunity) to nonvaccinated individuals through reduced viral transmission in the community1

(My emphasis, again)

Assuming this continues to hold up (and similar studies2 have found similar large reductions) it’s a striking example of herd immunity.

(Added later: The vaccine this paper looked at was RotaTeq.  This is not the vaccine that was recently found to be contaminated with porcine circovirus genomic fragments; that was the other rotavirus vaccine, Rotarix.)3

(Second update: RotaTeq apparently also is contaminated with porcine circovirus genomic fragments.)

  1. Curns, A., Steiner, C., Barrett, M., Hunter, K., Wilson, E., & Parashar, U. (2010). Reduction in Acute Gastroenteritis Hospitalizations among US Children After Introduction of Rotavirus Vaccine: Analysis of Hospital Discharge Data from 18 US States The Journal of Infectious Diseases DOI: 10.1086/652403[][][]
  2. For references see
    Weinberg, G., & Szilagyi, P. (2010). Vaccine Epidemiology: Efficacy, Effectiveness, and the Translational Research Roadmap The Journal of Infectious Diseases DOI: 10.1086/652404[]
  3. I haven’t talked about the Rotarix withdrawal because I think it’s been widely and very well covered on other blogs.  (I have 536 papers in my list of things I want to talk about here some time, so I usually don’t bother blogging about findings other places cover in detail.)  Vincent Racaniello at the Virology Blog has his usual high-quality commentary on it here.  He also made an important point on his podcast, This Week In Virology (either number 75 or number 77, I don’t remember which), which I don’t see explicitly on the post: The circovirus-containing vaccine went through all the safety trials, and no problems were seen.

    Obviously circovirus genomes aren’t supposed to be in the vaccine and they’ve got to go.  But (1) we don’t know if the genomes are infectious, or just fragments; (2) there’s no evidence, in spite of centuries of exposure to porcine circovirus, that it has any effects in humans; (3) the vaccines were shown to be safe, at least in the short term.

    On a larger scale, we’re entering a new era of analysis.  I suspect more of this sort of contamination will turn up as the sensitivity of our screening techniques improve, much like chemical detection: As we improve chemical detection to the parts-per-billion and parts-per-trillion level there needs to be better understanding of safety levels. Is this true for biologics? There are good arguments that there may be no safe level for some biologics, and any detection should lead to withdrawal, but on the other hand there clearly is a safe level for other biologics.  Human poop is loaded with vast amounts of viruses of peppers, for example; now that we know that should we regulate pepper mottle virus?

    I don’t have answers, which is why I relegate this to a footnote, albeit a long a rambling footnote.[]