Table 1.

2009–2010 H1N1 influenza pandemic timeline

H1N1 influenza timeline		H1N1 Vaccine timeline
	2009
CDC: respiratory samples from 3 children unsubtypable influenza A First “swine” flu-attributable death occurs (Oaxaca, Mexico)	April
>10,000 cases reported worldwide >98% of probable influenza cases testing positive for 2009 H1N1 2009 H1N1 virus isolated and identified as novel	May	Vaccine development begins
WHO declares pandemic (June 11)	June	Planning for vaccine distribution and administration
	July	Ongoing vaccine development, testing, production & planning for rollout
	August	NIH initiates clinical trials to determine vaccine safety and immunogenicity ACIP releases recommendations for vaccine prioritization
	September	4 vaccines against 2009 H1N1 influenza approved by FDA Healthy adults and older children found to need 1 dose of vaccine to generate strong immune response; children under 9 need two doses
Influenza activity peaks the second week of the month	October	3 million doses of nasal spray are the first vaccine ready for distribution 14.1 million doses are available by the end of October
CDC estimates H1N1 deaths among children and teens >500 Flu activity begins to decline late in the month	November	FDA approves a 5th vaccine against 2009 H1N1 influenza FDA authorizes an additional vaccine for use among infants and children 1 dose of vaccine is found to elicit a strong immune response among pregnant women >61 million doses of vaccine available by the end of the month
The number of states reporting widespread flu activity continues to decline	December	>93 million doses of vaccine are available Vaccination efforts expanded to the general public
	2010
	January
	February	FDA and WHO recommend that 2009 H1N1 be included in the 2010–2011 seasonal influenza vaccine ACIP recommends that all people >6 months of age receive yearly seasonal influenza vaccination Early vaccine expiration dates approaching
	March
Increased number of cases and hospitalizations in the southeastern United States	April	>80 million people vaccinated
	May
Southern Hemisphere reports of influenza A H3N2 and Northern Hemisphere reports of influenza B viral circulation exceed cases of 2009 H1N1	June
	July
WHO cancels pandemic declaration (August 10)	August