HOWKING: Když se začalo očkovat proti obrně, tak nebyla účinnost vakcíny ani 90%, i tak to byl ale průlom a začalo se ve velkém očkovat plošně.
I současná odolnost populace proti dětské obrně stále závisí ve velké míře na kolektivní imunitě. Rozhodně se tak nedá říct, že současná očkování proti "preventable diseases" je dokonalá.
Francis T et al (1955, as cited by Plotkin S et al 2008) conducted a major field trial in the USA in 1954 that
involved about 400 000 children, randomly assigned to IPV or placebo. A related, non randomized study by the
same authors involved another 200 000 children who were vaccinated and observed together with unvaccinated
children. Altogether, 71 cases of paralytic polio occurred in vaccinated individuals versus 445 among
unvaccinated individuals. In the placebo controlled trial, 11 cases of polio occurred among vaccines as compared
to 70 cases in the control group. The calculated vaccine efficacy was 80%-90% against paralytic polio and 60%-70%
against all types of polio.