Painless vaccines do not cause any adverse reactions like pain and fever and this term is associated with DTP vaccine which are subunit type of vaccines containing only a part of Pertussis causing bacteria and not the whole of it. They are called DTaP vaccines. The other type, DTwP vaccines causes slight fever, may cause persistent crying , pain in infants due to certain allergic reactions in response to inactivate whole cell component of Pertussis.
Recent research has shown that DTaP fails to prevent transmission and spread of Pertussis amongst people as it does not prevent Pertussis from entering and living inside the airways of vaccinated persons. So, the vaccinated persons are themselves immune but can still spread the disease to unvaccinated or people with weak immunity. Also DTaP provides lesser immunity than DTwP vaccine. This is the reason, DTaP vaccine /combinations should preferably be avoided for the primary series of infant immunization. There were recent news of Pertussis outbreaks in USA where DTaP vaccines are more common.
According to new IAP recommendations, DTaP vaccines should no longer be given to infants now. However in cases of severe allergies to DTwP vaccines, DTaP vaccine should be given.
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