The FDA has approved four vaccines for the prevention of swine flu. Recent preliminary reports from clinical trials of these vaccines have described common side effects encountered by participants. The first of the preliminary reports published is from a continuing study in Australia, where researchers are testing an inactivated H1N1 vaccine developed by CSL Ltd. in a group 240 volunteers. Following injection, 90% of recipients achieved a strong immune response within three weeks, a sign that the vaccine is working. Participants reported side effects that they experienced within 7 days. Another study tested an H1N1 vaccine developed by Novartis Pharmaceuticals with and without an oil-in-water adjuvant, known as MF29 in 175 adults.
Local Side Effects from Approved H1N1 Vaccines
No deaths or serious adverse events have been reported from any swine flu vaccine. Approximately 44% of participants reported mild side effects within 7 days of receiving the first dose of CSL's swine flu vaccine. 2.5% of vaccine recipients reported moderate local side effects, and there were no severe adverse events reported after immunization. 86% of the volunteers that received Novartis's H1N1 vaccine reported adverse reactions after one or both doses – the most common local side effect experienced was injection site pain. The reactions were generally mild or moderate and resolved after 72 hours. Reported local adverse events, or side effects occurring at the location where either vaccine had been administered, include the following:
- Tenderness
- Pain
- Redness
- Hardening of skin
- Swelling
- Bruising
Common Systemic Side Effects from Swine Flu Vaccines
Systemic effects were also reported by CSL and Novartis vaccine recipients. Approximately 36% of volunteers that received the swine flu vaccine manufactured by CSL experienced mild systemic side effects. 8% of vaccine recipients reported moderate systemic side effects, and less than 1% experienced a severe adverse reaction to immunization. Severe side effects reported include, malaise, muscle pain, and nausea. Muscle aches were the most common systemic side effect reported by participants receiving the H1N1 vaccine produced by Novartis, and no severe systemic side effects were reported. The following are common whole-body side effects occurring in response to either H1N1 vaccination.
- Headache
- Malaise (feeling out-of-sorts)
- Muscle pain
- Chills
- Nausea
- Fever
- Vomiting
In addition, researchers evaluated the occurrence of select adverse events including neurologic (e.g. Guillain-Barre syndrome), immune system or other serious reactions. According to the studies, none of the enrolled participants experienced these select events.
The National Institutes of Health (NIH) has also recently released preliminary safety informationfor an additional swine flu vaccine manufactured by Sanofi Pasteur Inc. Approximately 96% of healthy adults showed a robust immune response after receiving the vaccine. The only adverse events reported by trial participants were pain and redness at the injection site.
MedImmune LLC has received approval for a nasal spray H1N1 vaccine. While no safety data for this vaccine has been released to the public, MedImmune spokeswoman Karen Lancaster has reported that side effects are similar to those experienced with the nasal spray vaccine for the seasonal flu. Common events encountered by nasal spray vaccine recipients include runny nose, nasal congestion, and sore throat.
While preliminary reports show that approved swine flu vaccines have a low incidence of serious side effects, people can more accurately assess the relative risk of getting vaccinated for swine flu as more safety information from the studies investigating these four H1N1 vaccines is collected and made available to the public in the upcoming months.
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