Direction- Given are four sentence-paragraphs (S1-S4). S1 and S4 are given. From the given options (P, Q, R), choose two sentences which can be S2 and S3.

S1: The only way out of this pandemic, public-health officials say, is to use vaccines to achieve herd immunity, 

S2: _______________

S3: _______________

S4: both roughly 95% effective in protecting against the disease. 

P: The U.S. authorized two vaccines in mid-December: the first from Pfizer-BioNTech and the second from Moderna, 

Q: a type of biological fortress in which the vast majority of the population is protected against disease, blocking a roaming virus from finding new human hosts. 

R: But having an authorized vaccine isn’t the same as having a vaccinated public.