They also have this review (from July 2012) of the Washington State outbreak. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6128a1.htm
The main conclusion seems to be:
Quote:
Consistent with national trends, high rates of pertussis were observed among infants aged <1 year and children aged 10 years. However, the incidence in adolescents aged 13–14 years also was increased, despite high rates of vaccination with tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine, suggesting early waning of immunity.
This paragraph compares the vaccination status of people in the outbreak and the general population.
Quote:
Overall, 758 of 1,000 (75.8%) patients aged 3 months–10 years were up-to-date with the childhood diphtheria and tetanus toxoids and acellular pertussis (DTaP) doses. Receipt of Tdap was documented in 97 of 225 (43.1%) patients aged 11–12 years and in 466 of 604 (77.2%) patients aged 13–19 years. Estimated DTaP coverage in Washington among children aged 19–35 months was 93.2% for ≥3 doses and 81.9% for ≥4 doses in 2010; Tdap coverage in adolescents aged 13–17 years was estimated at 70.6% (3).
But not in a very clear way - so I tried to extract comparisons below. Not easy at all I have to say.....
Percent vaccinated Pertussis cases General population
3months -10 yrs 75.8% -
19-35 months - 81.9-93.2%
11-12 years 43.1%
13-19 years 77.2% 70.6% (13-17 yrs)
Looks like in young children (<10) quite significantly more unvaccinated (or not fully vaccinated) children got pertussis than those vaccinated (but the age ranges are not that same so I cannot say that with any certainty). The vaccination rate among 10-12 yr olds having pertussis is really low (43%!), but no comparison set is given. In older teenagers it seems vaccination status is irrelevent to if they get whooping cough (even might be slightly higher vax rates in those having the disease than in general - but the age group is slightly different and it may be within the statistical uncertainty).
This hints to me that vaccination exemptions might be having an effect on the outbreak among the younger children - and of course having more pertussis in circulation means the older children are more likely to encounter it.
And frankly that above is why I will continue to state that exemptions do play a role in these outbreaks. Unvaccinated children are more likely to catch pertussis if exposed to it (8 times according to this CDC article, but I've seen numbers of 9-23 times more likely) and if they catch it to have more serious illness and be infectious for longer (increasing the number of chances to pass on the disease). So even if it's not a major factor in the outbreaks, it's sure not helping to prevent them.
I also found this excerpt interesting.
Quote:
Unvaccinated children have at least an eightfold greater risk for pertussis than children fully vaccinated with DTaP (7). However, because in most of the cases the patients were vaccinated, the 4.5% of Washington school children who were exempted from vaccination during 2011–2012 represented only a small proportion of those at risk for pertussis in the state. Although vaccinated children can develop pertussis, they are less infectious, have milder symptoms and shorter illness duration, and are at reduced risk for severe outcomes, including hospitalization (8–10).
But we've gone way off topic from discussing responses to the congressional hearings. Perhaps we should start a new thread to debate the reasons for increased pertussis rates.... and leave this thread be.
My fault for bringing up pertussis. I was just trying to explain why Phil Plait was angry and why therefore he's sometimes not polite about choices to not vaccinate based on what he (and I for that matter) see as misunderstandings of the risks of vaccination.
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