No mercury, but a mercury-based compound called thiomersal that's used as a preservative. The WHO has submitted its findings on the existing literature.
The article [that suggests a link between mercury poisoning and thiomersal] has a number of limitations which undermine the conclusions drawn by the authors. These include: inaccessibility to the reader of the data on which the analysis was made; lack of clear case definitions for the conditions referred to in the paper; unclear or insufficient description of applied statistical methods; an assumption made by the authors that the toxicity of ethyl-mercury is equivalent to that of methyl-mercury, an assumption that cannot necessarily be made, and against which various authorities have warned; the assumption in the paper that the populations under study are the same (there is every possibility in the methods used of selection bias); and a failure to account for changing reporting patterns for diseases attributed to the vaccines over the years of the study. Published outcomes of the study regarding neurodevelopment and heart disease following administration of thiomersal-containing vaccines do not meet the scientific criteria required to suggest causal relationship. These points, taken together, lead GACVS to conclude that the paper provides insufficient evidence to warrant changes to public health policy.
thiomersal contains ethyl mercury, not methyl mercury.
Expert advice and data presented to the GACVS in June 2002 indicate that the pharmacokinetics of ethyl and methyl mercury are quite different. In particular, the half-life of ethyl mercury is short (less than one week) compared with that of methyl mercury (1.5 months). Two independent epidemiological studies completed in the United Kingdom of Great Britain and Northern Ireland suggest that there is no association between developmental delay, particularly adverse neurological developmental outcomes or behavioural problems, and thiomersal-containing diphtheria–pertussis–tetanus (DPT) vaccines.
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Rather than get flu shots why don't people just eat healthier and take precautions like wearing hats, scarves and carrying small bottles of sanitizer with them?
Herd immunity (or community immunity) describes a form of immunity that occurs when the vaccination of a significant portion of a population (or herd) provides a measure of protection for individuals who have not developed immunity. Herd immunity theory proposes that, in contagious diseases that are transmitted from individual to individual, chains of infection are likely to be disrupted when large numbers of a population are immune or less susceptible to the disease. The greater the proportion of individuals who are resistant, the smaller the probability that a susceptible individual will come into contact with an infectious individual.
Vaccination acts as a sort of firebreak or firewall in the spread of the disease, slowing or preventing further transmission of the disease to others. Unvaccinated individuals are indirectly protected by vaccinated individuals, as the latter will not contract and transmit the disease between infected and susceptible individuals. Hence, a public health policy of herd immunity may be used to reduce spread of an illness and provide a level of protection to a vulnerable, unvaccinated subgroup. Since only a small fraction of the population (or herd) can be left unvaccinated for this method to be effective, it is considered best left for those who cannot safely receive vaccines because of a medical condition such as an immune disorder, organ transplant recipients, or people with Egg Allergies.
The proportion of immune individuals in a population above which a disease may no longer persist is the herd immunity threshold. Its value varies with the virulence of the disease, the efficacy of the vaccine, and the contact parameter for the population. No vaccine offers complete protection, but the spread of disease from person to person is much higher in those who remain unvaccinated. It is the general aim of those involved in public health to establish herd immunity in most populations. Complications arise when widespread vaccination is not possible or when vaccines are rejected by a part of the population. As of 2009, herd immunity is compromised in some areas for some vaccine-preventable diseases, including pertussis and measles and mumps, in part because of parental refusal of vaccination.
Herd immunity generally applies only to diseases that are contagious. It does not apply to diseases such as tetanus (which is infectious, but is not contagious), where the vaccine protects only the vaccinated person from disease. Nor does it apply to the IPV poliomyelitis vaccine that protects the individual from viremia and paralytic polio but does not prevent the fecal-oral spread of infection. Herd immunity should not be confused with contact immunity, a related concept wherein a vaccinated individual can 'pass on' the vaccine to another individual through contact.
Basically, you get vaccinations not necessarily for yourself, but to help protect the segments of the population that are more vulnerable to the specific disease (mostly pregnant women, little children and the elderly).