Practice question

Oral polio vaccine OPV is classical example administered via oral route as drops rather than injection. Formulated by Albert Sabin in 1957 containing live attenuated poliovirus types 1,2,3 propagated in primary monkey kidney cells, stabilized with MgCl2, sucrose, buffered. Oral delivery mimics natural fecal oral transmission of wild poliovirus. Attenuated virus replicates in M cells of Peyer's patches, gut associated lymphoid tissue generating strong intestinal secretory IgA preventing colonization and transmission, plus systemic IgG and intestinal CD4 T cells. Advantages include easy administration by volunteers without training, low cost, non sterile technique, secondary spread to contacts via fecal shedding increasing community immunity, cold chain still required but thermostable formulations being developed. OPV contributed to near eradication reducing polio cases 99 percent since 1988. However rare reversion of attenuating mutations in 5'UTR and VP1 capsid leads to vaccine derived poliovirus VDPV causing paralysis and circulating cVDPV outbreaks, prompting switch to inactivated IPV in many countries. Other oral vaccines include rotavirus pentavalent, cholera WC-rBS, typhoid Ty21a illustrating mucosal immunity advantages.