More facts about vaccines....

In order to carry on with the theme of

Vaccine Awareness Week,

this post intends to selectively address some of the "talking points" made by anti-vaccination groups, mainly addressing misinformation about the immune system. If you know of any more facts, add them in the comments with appropriate links.

"Natural immunity is far superior to artificial immunity."

Natural immunity

is when immunity is acquired through non-intentional contact with an disease causing pathogen, while artificial immunity is acquired through deliberately inducing an immune response in the host. The

innate immune system

is present from birth and provides non-specific protection to the host without protective immunity, while adaptive immunity occurs from exposure to the disease causing agent whether via having the disease or being vaccinated.

Herd immunity

is when sufficient members of a population are immune and this prevents the spread of disease within a population, protecting vulnerable groups within it. Generally, this requires levels of 90-95% or more to be immune.

The idea that 'natural' immunity is superior to 'artificial' immunity comes in several forms - claims that artificially induced immunity is less long lasting than natural immunity, that vaccination bypasses the body's normal defences, that it's simply unnatural and 'damages' the immune system and that there are 'toxins' in vaccines that can cause harm. At times this comes packaged in with Germ Theory denialism, where it's claimed that germs don't cause disease at all.

Immune responses may not be of the same quality as natural infection but this depends on the antigen. However, vaccines use the same immune pathways as natural infections do to produce immunity. Some vaccines do not produce long lasting protection, but in many of those cases the diseases themselves tend to not do so as well. For example, for whooping cough naturally acquired immunity has been shown

to wane after 4-20 years with vaccines demonstrating a range of 4-12 years.

This known effect can inform policy when it's appropriate to provide further booster doses, but it's not an excuse to expose an individual to the known risks of the disease itself given that infant's immune systems are naive and it takes several days for them to generate an immune response on exposure to a pathogen. Vaccines do not provide 100% protection, but where secondary vaccine failure occurs due to waning immunity and an individual subsequently develops the disease the disease itself tends to be attenuated. To address the argument that vaccines damage the immune system a special article in "Pediatrics" provides a good discussion of this topic and why those concerns are not valid -

"Addressing Parents’ Concerns: Do Multiple Vaccines Overwhelm or Weaken the Infant’s Immune System?"

. There are many aspects to this, including that vaccines today contain much fewer antigens than in the past and that the capacity of the immune system of infants is easily able to deal with exposure to multiple antigens. The article also cites material that shows that children are not more likely to develop unrelated infections, and in fact are protected against severe infections from other pathogens that are more likely to occur in association with vaccine preventable bacterial and viral illnesses. There also doesn’t appear to be any increased risk of

more severe atopic disease (eczema) or allergies.

"Breast milk "boosts" the immune system and prevents infection"

Immunity against vaccine preventable diseases via the mother is mostly via

trans-placental transfer

of maternal IgG in the last few weeks of pregnancy and that is when maternal anti-bodies must be high. This passive immunisation usually persists for around 4-6 months and only provides immediate protection against some illnesses leaving the risk of being infected at a later stage.

Breast milk

can provide some protection particularly for gut infections such as Rotavirus, polio or cholera through transfer of IgA but this doesn’t extend to other infectious diseases such as Whooping cough. To build up immunity, infants have to have an infection or be vaccinated, which prompts the production of anti-bodies which protect against subsequent encounters with pathogens. Following on from this, it stands to reason that up until the point that a child stops being immunologically naive (at about age 6), they will be susceptible to just about any infection that they are exposed to, and that is a huge risk to take. Of particular concern are illnesses like

Whooping Cough,

where the effects can be devastating in infants under 6 months and there is little to no protection via maternal anti-bodies leaving the infant vulnerable to infection should they be exposed.

"A good diet is more effective at preventing disease"

I wish it was that easy, but while the concept that a good diet and other factors can assist in improving resistance to infections and additionally giving an individual more resources when they encounter a disease causing pathogen has some ground it doesn’t prevent illness of itself. If the immune system is functioning well already, there is no realistic way of boosting or enhancing this further. Even if this could be achieved it's likely this would prove to be undesirable as an over-stimulated immune system is the cause of autoimmune disease. This also ignores what is known of disease transmission and how the immune system works. Children are more susceptible to infectious disease as they have to have the illness in order to make the disease specific antibodies that will provide long-term immunity.

“Up to 90% of the total decline in the death rate of children between 1860-1965 because of whooping cough, scarlet fever, diphtheria, and measles occurred before the introduction of immunisations and antibiotics.” Archie Kalokerinos

This quote is fairly typical of the misinformation seen in anti-vaccination material. In this case there is a grain of truth as undoubtedly death rates did reduce prior to the introduction of vaccines with improvements in public health and medical treatments over the period of a century between 1840-1965. What you don't get told though is that death rates have little to do with incidence rates of infectious disease, nor morbidity (harm resulting from the disease itself). In addition, infectious disease comes in epidemics that have variable spacing but are typically between 2-7 years apart. This chart below demonstrates the sustained drop of infectious disease with the introduction of vaccination, from the 1950's onwards. Reference to the disease patterns of other vaccine preventable illnesses demonstrate a similar pattern. Given that during the period from the 1950's onwards measures to improve public health and modern medical treatment were already in place, it's clear that the introduction of vaccines worked to reduce disease incidence. A graph showing the reported incidence of measles from 1950 to the present. There were periodic peaks and valleys throughout the years, but the real, permanent drop coincided with the licensure and wide use of measles vaccine beginning in 1963.

(Source: Some common misconceptions about vaccination and how to respond to them.

A variation on this argument is that hygiene and sanitation were responsible for the disappearance of diseases. This may in part be true for some diseases transmitted by contaminated water such as Cholera but as can be seen by the non-disappearance of diseases like chicken pox which remain and cause epidemics every few years it's not going to have any effect on diseases transmitted by other means, such as droplet and faecal-oral. Other examples of this are

Tetanus,

where Clostridium tetani spores enter damaged tissue and

Measles

which is spread via respiratory means. In the case of

Polio,

which is transmitted by the oral-oral and faecal-oral routes, poorer sanitation before the 20th century meant that there was constant exposure to polio from an early age with an concurrent lower risk of developing paralytic polio. Then, paradoxically, improved sanitation increased the numbers of children and adults at risk of paralytic polio by reducing childhood exposure and thus immunity to the disease. Sanitation actually made things worse in that case.

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