Resurgence of pertussis in northern Portugal: two severe cases in very young children.

Between December 2004 and March 2005, two cases of pertussis (whooping cough) in unvaccinated infants, both under two months of age, were reported to the same municipal health authority in the north of Portugal. These cases are part of a changing epidemiological pattern of infection due to Bordetella pertussis in Portugal.

The Portuguese national vaccination programme’s recommended schedule includes five doses of diphtheria-tetanus-pertussis [1,2] whole cell (DTPw) pertussis vaccine. The first dose is recommended at two months of age and the fifth at 5-6 years of age [1]. Vaccine coverage in Portugal is high [3] and pertussis has been a statutorily reportable disease for many years. Reported cases of pertussis decreased since the 1960s and reached very low levels in the period 1993-2003 [4,5] (Table 1). In northern Portugal, fewer than 10 cases have been reported each year from 1993 to 2002 to zero cases in 2003; there was a clear resurgence in 2004, when 26 cases were reported (Table 1), with 2 deaths in children below 2 months of age. No deaths were reported from 2000 to 2003. Both in the north, and in Portugal as a whole, most reported cases occurred in the first year of life. In the northern region, most of these cases in the first year of life were observed in infants under the age of six months, and no cases occurred in the eleventh and twelfth months of life (Figure 1).