US imported chikungunya cases approach 400
The steady flow of imported chikungunya infections linked mainly to travel to the Caribbean continued in the United States last week, with 98 more cases reported, lifting the total to 398, the US Centers for Disease Control and Prevention (CDC) said yesterday.
All but six of the infections were associated with Caribbean travel, while five were connected to Pacific island destinations and two were linked to Asian travel, the CDC said. In an average year, only 28 imported chikungunya cases are reported in the United States.
Florida has had the most cases (105), followed by New York (44) and New Jersey (25). Imported infections have been reported by 37 states, two more than the previous week.
Only a few US locations have reported locally acquired cases, most of them in Puerto Rico, where the total grew by 6 to reach 199 last week, according to the CDC. Totals for Florida and the US Virgin Islands remained at two.
As of late last week, the Pan American Health Organization said the overall case count in the Caribbean epidemic was 469,620.
Jul 29 CDC update
Jul 28 CIDRAP News story "Caribbean chikungunya cases up 7%"
Study: Malaria vaccine prevented many cases in infants, small children
In a phase 3 trial, the experimental malaria vaccine RTS,S/AS01 prevented many cases of malaria in infants and young children in the 18 months after the third dose, particularly in areas of high malaria transmission, according to a report published yesterday by PLoS Medicine.
GSK, maker of the vaccine, announced last week its application for European Union approval of the vaccine, which could open the way to its use in Africa.
The study included 6,537 infants aged 6 to 12 weeks and 8,923 children aged 5 to 17 months who were randomly assigned to receive three doses of RTS,S/AS01 or a comparator vaccine. The trial was conducted at 11 sites in Africa.
Over the 18 months after vaccination, vaccine efficacy (VE) was found to be 45% (95% confidence interval [CI], 41%-49%) in children (5 to 17 months) and 27% (95% CI, 21%-33%) in infants, according to a Public Library of Science (PLoS) press release. Efficacy was highest in the first 6 months after vaccination.
The number of malaria cases prevented per 1,000 children varied by site, ranging from 37 to 2,865 for clinical cases and from –1 to 49 for severe cases, the report says. Cases prevented in infants ranged from –10 to 1,402 (clinical cases) and from –13 to 37 (severe cases).
"RTS,S/AS01 prevented many cases of clinical and severe malaria over the 18 months after vaccine dose 3, with the highest impact in areas with the greatest malaria incidence," the report says. "VE was higher in children than in infants, but even at modest levels of VE, the number of malaria cases averted was substantial.
As noted in earlier trial reports, more meningitis cases occurred in the malaria vaccine recipients than in the control group, but no causal relationship between the vaccine and the illness has been established, said an accompanying press release.
Jul 29 PLoS Med report
Jul 29 PLoS press release
Related Jul 24 CIDRAP News item
Meningococcal group C vaccine worked well in Canada, Netherlands
Two studies, from Canada and the Netherlands, released online yesterday in Clinical Infectious Diseases add to evidence that meningococcal serogroup C conjugate vaccine (MCCV) is highly effective in reducing the incidence of invasive serogroup C meningococcal (MenC) disease. They further suggest that the reduction in MenC carriage with vaccination provides herd immunity.
The Canadian findings were based on active, population-based surveillance of MenC in children and adults conducted by the Canadian Immunization Monitoring Program, ACTive (IMPACT) from 2002-12. The authors found that the proportion of all invasive meningococcal disease accounted for by MenC decreased from 30% in 2002-05, the period during which MCCV was introduced, to 8.5% in 2009-12.
Furthermore, after introduction of MCCV the incidence of MenC decreased from between 0.07 and 0.25 cases, depending on province, to 0.05 cases per 100,000 population per year, with a 14% rate of decline per year.
The reduction was significant despite different immunization schedules in different provinces, say the researchers. They also found that the largest reduction in incidence (from 0.27 to 0.05 per 100,000 per year, equaling 83%) occurred in 15- to 24-year-olds. This age-group was not vaccinated in all provinces, indicating that herd immunity played a role.
The currently recommended schedule for MCCV in Canada is zero to three doses before age 1, one dose at age 12 to 23 months, and one dose at 12 to 24 years.
Said the authors, "This study has provided clear evidence that this vaccine likely induced herd immunity by reducing the transmission of N. meningitis, protecting those in the population who were not vaccinated and likely provided longer lasting population protection by prevention of meningococcal carriage."
The nationwide study from the Netherlands found that in the decade after 2002, when MCCV was introduced in the country, the incidence of MenC disease was reduced by more than 93%. More than 36% of the reduction occurred in the unvaccinated population, and it lasted for 10 years or more, indicating that herd protection from reduced carriage of virulent meningococci is an important part of the effectiveness of MCCV.
Jul 29 Clin Infect Dis Canadian study abstract
Jul 28 Clin Infect Dis Dutch study abstract