id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-270858-ozvdz9ew	Altmann, Daniel M	What policy makers need to know about COVID-19 protective immunity	2020-04-27		.txt	text/plain	1563	90	49	Strategies in various countries that aim to stagger return to work on the basis of disease severity risk and age do not take account of how exposing even lower-risk individuals, such as young people with no comorbidities, to the virus so as to increase herd immunity can still result in pandemic spread. A caveat is that most studies, either of SARS survivors or of COVID-19 patients, have focused on people who were hospitalised and had severe, symptomatic disease. Anecdotal reports of reinfection from China and South Korea should be regarded with caution because some individuals who seemed to have cleared SARS-CoV-2 infection and tested negative on PCR might nevertheless have harboured persistent virus. 16 On the basis of this estimated R 0 , the herd immunity calculation suggests that at least 60% of the population would need to have protective immunity, either from natural infection or vaccination.	./cache/cord-270858-ozvdz9ew.txt	./txt/cord-270858-ozvdz9ew.txt