Pertussis in the unvaccinated
This is a study by James Cherry, generally considered to be the world’s leading expert on pertussis. This paper explores how pertussis presents in unvaccinated infants and children.
From Pediatrics:
The data collected in this study allow a precise description of selected aspects of pertussis as they occur in unvaccinated children. Clinical characteristics of the cough episodes were obtained at two time points: on the day the NPS was taken and 6 to 8 weeks later. At the time of the first assessment, 82.4% of patients had paroxysmal cough, and the majority also had posttussive vomiting, whereas only 5.7% had fever 38°C. In spite of the high prevalence of paroxysmal cough and posttussive vomiting, almost half of the patients were not initially considered to be probably or definitely pertussis by the treating physicians.
This looks like the odds of having complications, should an unvaccinated infant under 6 months old catch it:
Complications were observed in 95 of 1640 (5.8%) patients (Table 2). They were significantly more frequent in infants <6 months of age than in patients >6 months of age (23.8% vs 5.1%; P < .001). Most common complications were pneumonia (29.5%) and apnea (12.6%). Of all infants 6 months of age, 3.2% and 15.9% were reported to have pneumonia and apnea, compared with 1.6% and 0.1% in patients >6 months of age, respectively. There were no seizures reported in this study;
So three fourths of the time, if your baby under 6 months catches it, you still won’t have complications. Other interesting factoids from the study:
From October 1990 to September 1996, 20 972 specimens were submitted, and B pertussis was isolated in 2592 instances (12.4%).
Of the culture-proven cases, 50.7% were female, and the age range was 6 days to 41 years, with a mean and median of 4.3 years and 4.1 years,
respectively.
So there’s a 50% probability that an unvaccinated child will catch pertussis by age 4. Around age 4 is the average age of infection.
And the severity in the unvaccinated:
Of unvaccinated patients, 90.2% had paroxysmal cough, 78.9% demonstrated whooping, and 53.3% presented with posttussive vomiting; 5.7% had fever 38°C. The duration of cough was 4 weeks in 37.9% and 3 weeks in 17.4%
Interestingly…this:
90.2% had paroxysmal cough
…means one in 10 unvaccinated kids don’t get “the cough” at all when they catch pertussis. A few kids get REALLY lucky.