Originally Posted by Mut
How long has the flu shot been around? Has it even had time to establish that it works? The FDA does a poor job of screening drugs. Do you rely on the FDA and/or drug company to tell you that it works?
studies performed every year on the efficacy of the flu shot. Here's a link to the CDC: Flu vaccine effectiveness
"How effective is the inactivated influenza vaccine (IIV)?
Overall, in years when the vaccine and circulating viruses are well-matched, influenza vaccines can be expected to reduce laboratory-confirmed influenza by approximately 70% to 90% in healthy adults <65 years of age. Several studies have also found reductions in febrile illness, influenza-related work absenteeism, antibiotic use, and doctor visits.
In years when the vaccine strains are not well matched to circulating strains, vaccine effectiveness can be variably reduced. For example, in a study among persons 50-64 years during the 2003-04 season, when the vaccine strains were not optimally matched, inactivated influenza vaccine effectiveness against laboratory-confirmed influenza was 60% among persons without high-risk conditions, and 48% among those with high risk conditions, but it was 90% against laboratory-confirmed influenza hospitalization (Herrera, et al Vaccine 2006). A study in children during the same year found vaccine effectiveness of about 50% against medically diagnosed influenza and pneumonia without laboratory confirmation (Ritzwoller, Pediatrics 2005). However, in some years when vaccine and circulating strains were not well-matched, no vaccine effectiveness can be demonstrated in some studies, even in healthy adults (Bridges, JAMA 2000). It is not possible in advance of the influenza season to predict how well the vaccine and circulating strains will be matched, and how that match may affect the degree of vaccine effectiveness."
Now for the varicella vaccine (chickenpox and shingles):
Originally Posted by Mut
What about the vaccine for chicken pox? I was told by a respected physician that the vaccine only protects you for a period of years and that once it wears off you are susceptible to acquiring the adult version (shingles??) which is much worse.
That physician would have been correct about being susceptible to shingles later in life if varicella immunity were to wear off. Unfortunately, anyone who has ever gotten chickenpox the good old-fashioned way is also at risk. When someone gets chickenpox they eventually fight it off and their symptoms go away forever. The varicella virus, however, is not eliminated from the body, instead burrowing into sensory nerve roots and going dormant. Later in life the varicella virus can "reawaken" when disease, stress, or aging compromise the immune system. Although you won't develop chickenpox, the virus can irritate the nerve pathway, causing shingles.
The only way you can be sure you won't ever get shingles is to get immunized for varicella before you ever get chickenpox, and somehow maintain that immunity. No virus, no shingles.
"Is waning immunity a problem with the varicella-containing vaccines?
The length of protection/immunity from varicella-containing vaccines remains unknown. Available data from follow-up of children vaccinated in prelicensure clinical trials indicate that protection from varicella vaccine lasts for at least 25 years (Japanese data) and 14 years (U.S. data). However, most of the data concerning vaccine efficacy and persistence of antibody in vaccinees are based on research that was conducted when natural varicella infection was highly prevalent and had not been affected by wide use of the vaccine. A recently published community-based study among children 12 months to 12 years of age suggests that 1 dose vaccine-induced immunity to varicella may wane over time. Experience with other live viral vaccines (e.g., measles, rubella), however, has shown that post vaccination, immunity remains high throughout life. For these vaccines, second doses are needed to cover the small percentage of people who fail to seroconvert after the first dose (primary vaccine failure). Follow-up studies are continuing to assess levels of immunity in vaccinees as disease incidence declines."
Like so much based on the scientific method, vaccines are an inexact science. Everything we know is based on the preponderance of evidence, and is therefore constantly changing. The evidence right now says that vaccines are a much better option than gaining immunity from the live pathogens. It's all a risk/benefit analysis.