Immunisation: Why we do it and how ‘herd immunity’ works

Denial of community immunity or herd immunity is a common feature of antivaccinationists.

In fact groups that spread harmful disinformation, such as the Australian based Australian Vaccination-risks Network (AVN), have for years been refining the denial of this evidence based fact. Notably they misrepresent what herd immunity is, primarily by referencing an aspect of herd immunity or an expected result of herd immunity.

The Australian Government Department of Health offer this definition;

If enough people in a community are immunised against an infectious disease, there is less of the disease in the community, which makes it harder for the disease to spread.

Immunisation protects both people who are vaccinated and also helps the entire community. It helps protect those who are too young to be vaccinated and those who can’t be vaccinated for medical reasons. This is known as community (herd) immunity.

Claiming that the “laws” of No Jab No Pay and No Jab No Play “are based on herd immunity”, Meryl Dorey of the AVN contends;

The theory claims that the unvaccinated are more likely to contract and transmit diseases than their vaccinated peers.

Travel to a largely unvaccinated country, get shots and you’re apparently in a protected bubble. Back home and they’d have us believe we need a 95 per cent plus vaccination rate to be protected and that a lone unvaccinated individual can be responsible for an epidemic.

Indeed rather than “claim” that unvaccinated community members will contract and transmit disease, herd immunity provides greater protection for the unvaccinated. Nonetheless herd immunity cannot protect any particular unvaccinated individual and is very important with respect to protection from measles infection.

This is why individuals who cannot be vaccinated for specific reasons or those with weakened immune systems will be better protected in a community that has a vaccination level of 95% or above. In certain communities where vaccination levels are low, herd immunity and the cluster of immune individuals doesn’t exist. In this instance measles can easily spread from an infected individual to unvaccinated individuals.

If not for herd immunity providing protection to those who refuse vaccination and deny their children the protection of vaccine induced immunity, many of the false beliefs held by antivaccinationists could not persist. The success of so-called natural remedies, homeoprophylaxis and so on persist simply due to the protection of herd immunity.

  • The video below was produced by the BBC and provides an accurate summary of vaccination and herd immunity.

Immunisation: Why we do it and how ‘herd immunity’ works – © BBC News

Discredited anti-vaccine conspiracy theorist Judy Wilyman has even used denial of herd immunity in her ongoing attacks on Australia’s successful vaccination policy. Wilyman wrongly contends that only public health reforms such as sanitation led to the control of vaccine preventable diseases.

Vaccines did not create herd immunity to control infectious diseases, is an open letter on her website. The monumental flaw in her fallacious claim begins with her use of only mortality, and no morbidity data.

Also, Wilyman refers to changes in public health occurring before 1950. This ignores more modern vaccines such as that for Haemophilus influenzae type b (Hib) used in Australia from 1993 and later in Kenya from 1999.

Only vaccination can explain the control of Hib and the emerging success of the HPV vaccine.

The problem of clustered drops in herd immunity

There are many reasons anti-vaccine lobbyists push the falsehood that herd immunity “is a myth”, is not important or simply doesn’t exist.

To listen to recent untruths from Meryl Dorey, one should eagerly accept that it is “documented” in peer reviewed literature as being more or less non-existent. Indeed, “it is a lie” lies Dorey. By essentially mocking the importance of herd immunity, garden variety anti-vaccine tricksters can shirk the responsibility that not vaccinating may harm the wider community, innocent infants or children, and deny larger scale resistance to infection that the immune-compromised rely on.

Herd immunity is an impressive function of mass vaccination. More so it is remarkably easy to understand. But the anti-vaccine lobby refuse to accept any need for or benefit from, mass vaccination. It is even more bizarre when one considers the parallels to so-called “natural immunity” – such as with marvellous measles, or “right of passage” infection and immunity. With mass vaccination we can control the spread of immunity and thus the spread and ultimate impact of vaccine preventable disease.

We should never forget that claims of raising impeccably healthy and disease-free unvaccinated children can exist only for as long as vaccine-induced herd immunity remains at a crucial level. The level that permits a free ride and protection from most vaccine preventable diseases for these very children.

Once again the formula frequently relied upon is “< 100% = 0%” – such as this 1973 article. One popular mode is that if a child is vaccinated against X, they should be safe from infection with X. Even worse is a distortion of epidemiological factors at play. This involves citing nationwide or statewide vaccination rates – which level out as reasonably high – along with reported outbreaks, such as those seen of pertussis or measles. Or including individuals who have had just one MMR jab (in the case of measles) or those whose vaccine-induced pertussis immunity has certainly waned.

This not-very-clever deception ignores the fact that areas with low vaccination uptake provide the ideal conditions for infection to spread rapidly.

The video below compares the difference in infection spread in the sparsely located unvaccinated compared to a cluster of unvaccinated individuals.

Herd Immunity