Rotavirus vaccine strain can infect others

A recent report documents the transmission of Merck's RotaTeq rotavirus vaccine. The live vaccine was passed from a vaccinated infant to an older unvaccinated sibling; this resulted in a severe gastroenteritis that required emergency department care. It appeared that the vaccine strain virus mutated and may have become more dangerous.
This is not the only live vaccine that can be transmitted to those around the unvaccinated child. It is well recognised that the chickenpox (varicella) vaccine can be transmitted from vaccinated children; in one case a pregnant woman caught chickenpox from her vaccinated child. Children receiving some forms of mumps vaccine can also be infectious, though this is not known to happen with the Jeryl Lynn or RIT 4385 strains of mumps vaccine used in the MMR.
One has to question the wisdom of mass vaccination in developed countries against an illness such like rotavirus which is virtually never life-threatening in the wealthier countries of the world. This new case report highlights the potential problems of mass vaccination against diseases which are generally mild, with the risk that vaccination will merely make a relatively harmless illness more dangerous. We are already seeing this with mumps where vaccination (with a not very effective vaccine) is pushing the illness into older age groups in whom complications are more common.

Added 29 April 2010