id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-296935-y77c4ro4	Couch, Robert B.	Prior Infections With Seasonal Influenza A/H1N1 Virus Reduced the Illness Severity and Epidemic Intensity of Pandemic H1N1 Influenza in Healthy Adults	2011-11-10		.txt	text/plain	3992	205	48	Serum antibody to the pH1N1 and seasonal A/H1N1 viruses was measured in 579 healthy adults at enrollment (fall 2009) and after surveillance for illness (spring 2010). Preexisting antibody to pH1N1 virus, responses to a single vaccine dose, a low infection-to-illness ratio, and a short duration of illness and virus shedding among those with influenza indicated presence of considerable preexisting immunity to pH1N1 in the population. To assess the clinical and epidemiological impact of pH1N1 infections and to identify immunologic factors correlating with infections and illnesses, we conducted a prospective study of influenza in a young adult population. Occurrences of pH1N1 influenza infections and illnesses in relation to serum HAI antibody titer at enrollment are shown in Table 2 . When the retrospectively identified moderate to severe ARIs with a significant antibody response were included, the inverse correlation between baseline titer and frequency of pH1N1 infection and illness was significant (v 2 for trend, P 5 .01).	./cache/cord-296935-y77c4ro4.txt	./txt/cord-296935-y77c4ro4.txt