06/03/2026
Many parents are surprised to learn that transmission and vaccine effectiveness are often more nuanced than public messaging suggests.
For some diseases, vaccinated individuals can still become infected and transmit the illness, sometimes with mild or no symptoms. This has been documented in CDC materials and peer reviewed medical literature.
As Physicians for Informed Consent summarizes:
“Children vaccinated with the diphtheria, tetanus, and pertussis (whooping cough) vaccine (DTaP) or the inactivated polio vaccine (IPV) can still be infected with diphtheria-causing bacteria, pertussis bacteria, or poliovirus and spread them to others, even with mild or no symptoms of their own. [10-13] The influenza vaccines (TIV and LAIV) have not been observed to significantly reduce the spread of influenza. [14,15] About half of schoolchildren vaccinated with the measles, mumps, and rubella (MMR) vaccine can still be infected with measles virus and spread it to others, even with mild or no symptoms of their own. [16-19] Several studies of the COVID-19 vaccine suggest that the vaccine has had no measurable impact on preventing transmission. [20-22]”
This does not mean vaccines have no effect. It means transmission risk is more complex than vaccine status alone.
For additional citations and source references on this topic, see Reason #4 in the resource below. It explains why vaccine status alone does not determine whether someone can catch or spread certain illnesses:
https://physiciansforinformedconsent.org/immunocompromised-schoolchildren/
