Although mild side effects are reported in about half of 2009 H1N1 vaccine recipients, reports of widespread serious adverse events are not forthcoming. Thus, the vaccine – which was prepared according to the same standards and protocols as previous influenza vaccines – appears to be safe.
However, many people who are still concerned about reports of potential problems with the “new” vaccine – and individuals who are frustrated that there isn’t enough to go around – might benefit from additional information regarding the available vaccine preparations.
The Food and Drug Administration Has Approved Four H1N1 Vaccine Preparations
Of the 2009 H1N1 vaccine preparations currently available, three contain the inactivated, or “killed,” virus, and one contains an attenuated, or weakened, form of the live virus. The different preparations and their suppliers are as follows:
- MedImmune: Contains attenuated live virus; contains no mercury; available as a nasal spray; indicated for persons aged two years to 49 years.
- Sanofi: Contains inactivated virus; single-dose vials contain no mercury; multidose vials (10 adult doses) contain 25 micrograms of mercury per adult dose; administered as an intramuscular injection; indicated for persons aged six months and older (mercury-free dosage is the only form available for children younger than three years).
- Novartis: Contains inactivated virus; single-dose vials contain less than one microgram of mercury; multidose vials (10 adult doses) contain 25 micrograms mercury per adult dose; administered as an intramuscular injection; indicated for persons aged four years and older.
- CSL Biotherapies: Contains inactivated virus; single-dose vials contain no mercury; multidose vials contain approximately 25 micrograms mercury per adult dose; administered as an intramuscular injection; indicated for persons older than 18 years.
Precautions and Recommendations for Administering 2009 H1N1 Vaccine
Due to the methods used to prepare influenza vaccines, all 2009 H1N1 influenza vaccine formulations contain residual egg protein. Persons with a bona fide egg allergy should not receive these vaccines.
None of the 2009 H1N1 preparations contain an adjuvant (adjuvants are materials that are designed to boost the response to a vaccine by alerting the immune system to the presence of a foreign invader; they can lead to more pronounced side effects).
Although many experts now believe that one dose of vaccine is sufficient for all age groups, current guidelines still recommend that persons from six months of age through nine years receive two doses separated by three to four weeks.
45 – 50% of all vaccine recipients will experience pain at the injection site (for intramuscular preparations), body aches, headache, or malaise.
High-risk groups – those who should receive the vaccine first – include:
- Healthcare workers, emergency medical personnel, and other first responders
- Pregnant women (should receive inactivated forms of the vaccine)
- Individuals aged six months to 24 years
- People from 25 to 64 years of age who have chronic diseases (e.g., diabetes, heart disease, lung disease, immunodeficiency, etc.)
- People who care for infants younger than six months of age
Individuals who should not receive influenza vaccination include those with:
- A history of previous Guillain-Barré syndrome
- A history of egg allergy or severe (i.e., life-threatening) reaction to previous influenza vaccination
- Severe illness (i.e., pneumonia, high fever, etc.); mild upper respiratory infection (e.g., a cold) is not a contraindication to immunization
Special Information Regarding the Live Attenuated H1N1 Influenza Vaccine (MedImmune Nasal Spray)
Since MedImmune nasal spray contains a live virus, its use carries some special precautions.
Individuals who should not take the nasal influenza vaccine include:
- Immunosuppressed persons (diabetics, HIV/AIDS, chemotherapy, transplant patients, etc.)
- People who live with immunosuppressed persons
- People with severe allergy to eggs
- People with chronic medical conditions (heart, lung, kidney, or liver disease; asthma; diabetes; etc.)
- Children and adolescents on long-term aspirin therapy (e.g., those with Kawasaki disease)
- Children who have asthma or who have experienced wheezing within the past year
- People with neurologic conditions that interfere with breathing or swallowing
The 2009 H1N1 nasal spray should not be administered concurrently with seasonal flu nasal sprays; it can be administered at the same time as intramuscular preparations, however.
Individuals who receive the nasal spray may shed the live virus for up to three weeks. While it is unlikely that other healthy persons will become infected from viral shedding, people with weakened immune systems may be at risk from exposure to immunized individuals.
While the absolute efficacy of the 2009 H1N1 nasal spray is not yet known, a study done in 2008 showed that the seasonal flu nasal spray was less effective than injected preparations for preventing influenza. (Monto A, et al. Comparative efficacy of inactivated and live attenuated influenza vaccines. N Engl J Med. 2009;361:1260-67)
The vaccine for 2009 H1N1 appears to be safe and effective. Persons at high risk should be immunized as soon as possible; other individuals who feel comfortable doing so should be immunized when sufficient supplies of vaccine are available.
(Adapted from Bartlett G. 2009 H1N1 influenza – just the facts: vaccine essentials. Medscape Today. November 5, 2009)
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