I looked into this, and it does seem the vaccine reduces transmission. It just doesn’t stop it entirely. The paper below is Wikipedia’s source. Upon a close read, in the daycare there were three groups of vaccinated children:
* Those positive for antibodies but pcr negative —> had been exposed, cleared virus without infection
* those pcr positive but asymptomatic
* those pcr positive and symptomatic
About 30% were in the seropositive group which didn’t have pcr positivity. So it seems like transmission was reduced at least 30%. It’s also possible the other two groups would have had lower transmission rates than if they had had no vaccine.
If you have a more precise source I’d be interested to see it, but if this is the worst case it’s pretty good!
> We used PCR, EIA, and culture to confirm B. pertussis infection in two highly vaccinated groups of children in two day-care centers. Three (10%) of 30 2- to 3-year-old children were seropositive for recent infection; one had nasopharyngeal colonization and a clinical illness that met the modified WHO case definition. In the day-care center for the 5- to 6- year-old group, 9 (55%) of 16 children were IgM positive, 4 (25%) of whom had nasopharyngeal colonization. Of these four children, three had nonspecific cough, and only one met the modified WHO definition for pertussis. None of the children in our study, including those who met the WHO definition, had been examined by a physician before our investigation.
>Children who were seropositive and re- mained both asymptomatic and PCR negative probably had sufficient immunity from vaccines or natural boosters to protect them against persistent colonization and clinical disease. Their seropositivity could not be due to vaccine because the children were tested more than a year after having been vaccinated.
Whooping cough - that treats the symptoms but does not stop the patient from spreading the disease
Edit: Added context