‘Definitely effective‘ vaccines would presumably be ones associated with disease eradication. For e.g., thefor ( ), and for ( , ). Yes, it definitely bears remembering that diseases that were scourges as recently as the middle of the 20th century are no longer with us either entirely or almost so, thanks largely to vaccines.
The acellular version of thecould be considered an example of a less effective vaccine. Several industrialized countries (Australia, Canada, Western Europe, USA) switched to this version from its more effective whole-cell counterpart, largely based on perceived safety concerns. However, 20+ years of data now show pertussis resurgence associated with acellular vaccine usage in countries that switched ( ), implying such a change may not have been judicious.
Therequires annual immunization simply because it is prepared anew each year based on assessments of which flu strains are circulating in that given year. Thus, the main drawback of current flu vaccines is they aren’t universal, i.e., one vaccine doesn’t protect against all or even many flu strains. As well, a of flu shot efficacy in the US from 1967 to 2011 found they were only 67% efficacious ( ). This is partly because flu shot efficacy can vary considerably from year to year, given that the flu vaccine changes from year to year.
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