( CNN ) -- Days after the U.S. government announced upcoming trials for an H1N1 flu vaccine , Saint Louis University has been inundated with phone calls and e-mails from people volunteering for the study . Concern about the H1N1 virus grew after it spread quickly around the globe earlier this year . The university 's Center for Vaccine Development has received more than 500 responses from potential volunteers since Wednesday , when the National Institutes of Health ( NIH ) announced human trials for a swine flu vaccine would begin in early August . `` This response has been exceptionally strong , '' Nancy Solomon , a spokeswoman for the university 's medical center , told CNN Radio . `` We have n't had that strong of a response to our call for volunteers since we conducted our small pox vaccine research after September 11 . '' Thousands of Americans are currently being recruited for swine flu vaccine testing at several research centers across the country , including Saint Louis University 's Center for Vaccine Development . `` The federal government comes to us when they need a quick response to test the safety and efficacy of vaccines , '' Solomon said . Other trial sites include the University of Maryland Medical Center in Baltimore ; Baylor College of Medicine in Houston , Texas ; Cincinnati Children 's Hospital Medical Center ; Emory University in Atlanta , Georgia ; Group Health Cooperative in Seattle , Washington ; The University of Iowa in Iowa City ; and Vanderbilt University in Nashville , Tennessee . They will be joined by Children 's Mercy Hospital in Kansas City , Missouri ; Duke University Medical Center in Durham , North Carolina ; and IPS Research in Oklahoma City , Oklahoma . Most of the human trials are being funded by the National Institutes of Health . In an effort to deliver the vaccine to those who will need it most by October , the clinical trials will enroll as many as 1,000 adults and children , according to officials at the National Institute of Allergy and Infectious Diseases , a division of the NIH , which will lead the effort . The trials will measure the safety and effectiveness of the vaccine . The research is a first step toward U.S. health officials ' goal of developing a safe and effective vaccine against H1N1 , also known as swine flu , which has been declared a global pandemic by the World Health Organization . After careful screening , volunteers will be inoculated and asked to keep a diary on how they feel . After eight days their blood will be checked . After 21 days they will receive another dose , followed again by diary logs and blood tests . Patients will be monitored two months for safety issues , followed by a four-month and six-month checkup . `` The purpose of these trials is always to make sure they are safe , '' said Dr. Karen Kotloff , professor of pediatrics and lead investigator and researcher at Maryland 's Center for Vaccine Development . `` But even after six weeks , if things look good , we 're pretty sure the vaccine will work . '' At last count , the CDC said there are 43,771 H1N1 reported cases in the U.S. , along with 302 deaths that have been linked to the illness . In a normal flu season , about 36,000 Americans die from influenza and related complications . Models predict the 2009 H1N1 flu will peak in October , with many cases being diagnosed in September , according to Dr. Robert Belshe , director of Saint Louis University 's Center for Vaccine Development . `` We 'll be in the midst of it before we know it , '' Belshe said . Swine flu could sicken one in five people this fall , and Belshe said he worries that the number of serious health complications and deaths as a result of the H1N1 virus could soar . `` It 's looking more and more like we 're going to have a big flu outbreak this fall as soon as the kids get back to school , '' Belshe told CNN Radio . `` Influenza is unpredictable , but I believe this pandemic will hit pre-teens , teens and their parents hard , and as many as 60 million Americans could be sick with the flu . It 's critical that we find a way to protect people from this disease . '' CNN Radio 's Barbara Hall contributed to this report .
Saint Louis University has received more than 500 responses since Wednesday . Thousands of Americans being recruited for trials in dozen of sites across nation . Patients will be asked to keep progress while they are monitored for two months . Doctor says virus could sicken one in five people this fall and peak in October .