COVID Odyssey: Worldwide Winter Windup 10 ~ Vaccine hesitancy ~ is herd immunity possible?

The vaccine hesitant includes a range of people ranging from people fearful of getting a jab, those fearful of the consequences of getting a jab, to anti-vaxxers.

‘Herd immunity’, also known as ‘population immunity’, is the indirect protection from an infectious disease that happens when a population is immune either through vaccination or immunity developed through previous infection. WHO supports achieving ‘herd immunity’ through vaccination, not by allowing a disease to spread through any segment of the population, as this would result in unnecessary cases and deaths.

See:

https://www.who.int/news-room/q-a-detail/herd-immunity-lockdowns-and-covid-19

For more definitions see:

Welcome

A large theoretical literature shows how to derive R0 for
different infections, often implying that the 1 – 1/R0
threshold be used as a target for immunization coverage
and that its achievement can lead to eradication of target
infections.

See:

https://www.who.int/news-room/q-a-detail/herd-immunity-lockdowns-and-covid-19

Recent research into New Zealanders’ attitudes to vaccination suggest positions have become more polarised over the last decade, with 60% identifying as “vaccine believers” and 30% as “vaccine sceptics”.

https://theconversation.com/30-of-new-zealanders-are-vaccine-sceptics-so-trust-is-key-to-covid-19-vaccine-roll-out-151291

In New Zealand

The overall potential uptake, including those already vaccinated and those who are likely to get a vaccine is estimated to be 79%, from 77% in June, 80% in May and 77% in April. The difference from June is not statistically significant and the result should be regarded as “no change”.

https://www.health.govt.nz/our-work/diseases-and-conditions/covid-19-novel-coronavirus/covid-19-vaccines/covid-19-vaccine-strategy-planning-insights/covid-19-vaccine-research-insights

Similarly in the USA A study of more than 1,000 demographically representative participants found that about 22% of Americans self-identify as anti-vaxxers, and tend to embrace the label as a form of social identity.

According to the study by researchers including Texas A&M University School of Public Health assistant professor Timothy Callaghan, 8% of this group “always” self-identify this way, with 14% “sometimes” identifying as part of the anti-vaccine movement.

. . .

“The fact that 22% of Americans at least sometimes identify as anti-vaxxers was much higher than expected and demonstrates the scope of the challenge in vaccinating the population against COVID-19 and other vaccine-preventable diseases,” he says.

See:

‘Concerning’ number of Americans identify as anti-vaxxers

Below is a graph showing the percentage of the population that needs to get vaccinated to achieve herd immunity:

RoHerdGraph

This version may be easier to read:

HerdChart

Ro (R0) is the number of people that one person may infect on average in a population where no one is immune.

For the Delta variant of COVID-19 Ro has been estimated between 5 and 8 people.

We have used the same range to estimate Ro for the initial outbreak of COVID-19 in early 2020.

For the Delta variant we have estimated Ro to be between 9 and 12.75.

Regardless, when Ro = 5, from the graph, 80% of a population would need to be vaccinated to achieve herd immunity.

When Ro = 8, the percentage rises to 87.5%.

When Ro =9, we need almost 89% to be immunised.

When Ro =10, we have about 90% and when Ro = 12.75, over 92%.

The graph is created from this table:

RoHerdTable

Clearly herd immunity is unlikely even when Ro = 8 unless many of the vaccine hesitant get immunised or get a level of immunity when they get infected with COVID-19.

We do not wish anyone to get COVID-19.

At least half of the vaccine hesitant may need to get vaccinated before we get anywhere near a 90% vaccination level in New Zealand.

Do you think a 90% vaccination rate is achievable in NZ?

If you do think 90% is achievable, how soon do you think this may be achieved?

Also see the NZ Herald on Sunday 19 September p6:

Little90Herald

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