It seems that California faced this year the largest pertussis outbreak since 1959 affecting even people who had been previously vaccinated. The researchers from California Department of Public Health (CDPH) now believe that pertussis vaccine doesn’t have permanent effect.
Pertussis also called whooping cough or the 100 days’ cough is a disease caused by a bacterium (Bordetella pertussis) and is extremely contagious. The disease usually targets young people and infants. The coughing fits last about six weeks and there’s no effective treatment for pertussis. However, doctors recommend antibiotics to shorten bacteria’s life span.
A recent CDPH report shows that in the last 11 months in California were recorded 9,935 new cases of pertussis with 26.0 cases per 100.000. Californian health experts say that this was the largest Californian whooping cough outbreak in nearly 70 years.
Newborn were the most affected, but also teenagers aged from 14 to 16 that had been recently immunized through acellular pertussis vaccine (Tdap). These findings were published on Friday in the CDC’s Morbidity and Mortality Weekly Report.
Researchers say that adolescents contracted the pertussis bacteria although they had been vaccinated for diphteria, pertussis and tetanus at least 3 years before because their immunity obtained through the Tdap vaccine had started to wane.
The pertussis epidemic was not caused by lack of vaccination – 83 percent of adolescents have been vaccinated against it, while only 2.2 percent didn’t receive any Tdap vaccine doses.
In 2010, there was another pertussis epidemic with nearly 9.000 cases at a 24.6 cases per 100.000 rate. Back then this epidemic was recorded as the biggest pertussis outbreak in the last sixty years.
However, experts say that pertussis vaccines were not completely ineffective. Before any pertussis immunization, each year 157 new cases per 100.000 were recorded in the US.
In 2014, newborns younger than 1 year had a 174.6 rate per 100.000, while teenagers had a 137.8 rate per 100.000 fifteen-year-olds – an unusually high rate for this group of population, experts say.
The CDPH report also recorded pertussis incidence among infants and adolescents by their race and ethnicity. Non-Hispanic white children had a rate of 120.7 new cases per 100.000, Hispanic children recorded 207 cases per 100.000, while Asians had an incidence of 48.5 per 100.000. Black infants had similar rates with white ones.
White adolescents aged 14 to 16 had a considerable higher rate than Hispanic and Asians – 166.2 pertussis cases per 100.000 white teenagers as compared to 64.2 cases per 100.000 Hispanic adolescents or 43.9 per 100.000 Asian adolescents.
Doctors also recommend pregnant women to get a Tdap vaccine during the third trimester to boost infants’ immunity against the disease until their first vaccination at 2 months.