With H1N1 vaccine reaching the public early this month, it's good to know how this vaccine was developed and how it will protect people from H1N1 to make an educated decision on whether to get the shot or not.

The five vaccine manufacturers are CSL Limited, MedImmune, Novartis, GlaxoSmithKline and Sanofi Pasteur; first shipments of the vaccine were sent the week of Oct. 5. The H1N1 vaccine batches include a live attenuated vaccine to be given via nasal spray, and an inactivated vaccine to be given via injection. Kathleen Sebelius, secretary of the Department of Health and Human Services (HHS), said there will be enough vaccine for all U.S. citizens.

Vaccine Development

All five companies developed their vaccines in the same manner. H1N1 vaccine is developed no differently from regular seasonal flu vaccine, except it is a different strain of the flu, according to Gregory A. Poland, MD, MACP, FIDSA, director Mayo Vaccine Research Group and assistant editor for the Mayo Clinic Family Health Book: Fourth Edition.

"What happens is the virus is isolated from humans; then adapted to grow in eggs," Poland explains. "It takes weeks to do this," he continues. "Then the eggs are inoculated, the virus is harvested and inactivated. It's then split and the vaccine is produced. It's important to note this vaccine is simply a seasonal strain change and not a new vaccine."

Poland explains the seasonal flu vaccine formula changes slightly annually depending on which strains are prominent, but are developed the same way each year.

Clinical Trials

Even though development of the H1N1 vaccine is only slightly different from that of seasonal flu vaccine, Poland says much more surveillance is being done on H1N1 vaccine to ease people's concerns.

This surveillance is done by conducting clinical trials and monitoring patients after they receive the H1N1 vaccine. Clinical trial results have been promising, and Poland stresses there has been no serious side effects from the vaccine thus far.

Additionally, HHS recognizes getting the flu shot and then having an adverse health occurrence can be coincidental. The Associated Press reported Oct. 1, the government is starting a system to track possible side effects after the flu vaccination.

"Every day, bad things happen to people. When you vaccinate a lot of people in a short period of time, some of those things are going to happen to some people by chance alone," says Daniel Salmon, PhD, NVPO, a vaccine safety specialist at the HHS.

The idea of this surveillance system is to detect any rare but real problems quickly, and explain the inevitable coincidences that are sure to cause some false alarms. For example, if a patient has a heart attack a week after getting a flu shot, is it connected?

Flu

At this point, according to the CDC, potential side effects appear to be the same as those from the seasonal flu vaccine, such as soreness at the injection site, mild fever, body aches and fatigue. For the nasal spray vaccine, other side effects include runny nose or nasal congestion, sore throats in adults and fever in children ages 2 to 6.

An immune response to the virus develops 8-10 days after receiving the vaccine, just like in the seasonal flu vaccine, according to the CDC. Immune response is monitored through a blood test in clinical trials participants.

According to Michael G. Schmidt, PhD, director, Office of Special Programs, and professor and vice chair, department of microbiology and immunology, Medical University of South Carolina, Charleston, another result of the clinical trials showed that, despite original findings, adults and children ages 10 to 17 only need one dose (15 mcg) of the vaccine; children 9 and younger need two doses (ideally 4 weeks apart) to correlate immunity.

The National Institute of Allergy and Infectious Disease (NIAID) is conducting a clinical trial in pregnant women, who are thought to be especially susceptible to the disease. At the time of this writing, NIAID was enrolling 120 women in their second and third trimesters into this clinical trial. They will receive an initial injection and then a second injection 21 days later.

"Study investigators will take blood samples to determine how the immune system responds to the vaccine at set time points before and following each injection. Cord blood will also be collected to measure maternal antibodies transferred to infants through the placenta," a NIAID press release states.

Aside from pregnant women, other priority groups encouraged to get the vaccine first are children from 6 months to 18 years old; young adults ages 19 to 24 years old (mainly because of how fast H1N1 can spread throughout college campuses); caregivers and household contacts of children less than 6 months old. Those ages 25 to 64, who have an existing medical condition making them more susceptible to contracting H1N1, should also be vaccinated as well as health care and emergency medical personnel.

Two separate vaccines are necessary for protection from both H1N1 and seasonal flu and can be administered at the same time.