Vaccines are available to prevent a number of respiratory diseases, including influenza, S. pneumoniae infection, H. influenzae type B infection (in young children), pertussis, diphtheria, varicella, and measles.
The price-earnings ratio can be calculated as: Market Value per Share / Earnings per Share. For example, suppose that a company is currently trading at $43 a share and its earnings over the last 12 months were $1.95 per share. The P/E ratio for the stock could then be calculated as 43/1.95, or 22.05.
Jeremy Siegel has suggested that the average P/E ratio of about 15 (or earnings yield of about 6.6%) arises due to the long term returns for stocks of about 6.8%. In Stocks for the Long Run, (2002 edition) he had argued that with favorable developments like the lower capital gains tax rates and transaction costs, P/E ratio in low twenties is sustainable, despite being higher than the historic average.