Why herd immunity could be achievable despite anti-vax attitudes
Three recent studies suggest a substantial majority of UK adults are ready to be vaccinated against Covid-19, making herd immunity possible, and potentially banishing the coronavirus pandemic to the realm of bad memories and fever-dreams. If 79% of UK adults receive an effective vaccine, this would match or surpass the hypothetical threshold scientists expect a population typically needs in order to defeat a disease like Coronavirus.
Aneesh Thakur, assistant professor of vaccine design and delivery at the university of Copenhagen, though quick to caution against making generalisations, explained that the ‘R’ number has a crucial role to play in how much of the population needs to be vaccinated to ensure success:
Assuming that on average [the ‘R’ number] is 2.5-3, then around 70% of the population should be vaccinated to get herd immunity in order to prevent further spread within the population. We cannot generalise, but that is a theoretical estimation.”– Professor Aneesh Thakur, university of Copenhagen, September 2020.
It appears that a substantial proportion of the UK public is ready to put their trust in a vaccine, meaning that it would be possible to meet this theoretical threshold. Comparing data from surveys conducted by King’s College London, YouGov, and University College London, a clear pattern of positive attitudes to taking a coronavirus vaccine emerges. In contrast to widespread media coverage of anti-vax attitudes in the national press, most recently in response to the figures released by UCL, a significant majority of respondents signalled that they were ready to get vaccinated:
Survey results per study – KCL / YouGov / UCL:
UCL Covid-19 Social Attitudes Survey:
The largest and most recent dataset shown above is the landmark study conducted by University College London, sponsored by the Nuffield foundation, which has been tracking the psychological and social impact of the pandemic on a weekly basis since the original Coronavirus lockdown began. Their evidence overwhelmingly suggests that “on balance”, a significant majority of UK adults have a positive attitude to taking a Coronavirus vaccine. Nearly 80% of UCL survey respondents, taken from a sample of over 70000 people, said that they were very likely, moderately likely, or more likely than not to take a safe, effective vaccine against Covid-19:
Chart: Miguel Roca |Fri 25 Sep 2020 | Getthedata
As confirmed cases of Coronavirus rise exponentially across the UK and parts of Europe, society must pin its hopes of stopping the pandemic on an effective vaccine. Estimates for a successful vaccination strategy which could lead to safe and effective herd immunity range from between 43% and 67% of the global population, meaning that an 80% vaccination rate should comfortably meet the required target to put the brakes on the pandemic.
Whilst the estimated “threshold” for herd immunity differs considerably between different diseases, and exists within a hypothetical range, if a sufficiently high proportion of the UK adult population were immunised against Covid-19, it should comfortably match the threshold for related diseases such as SARS1 and influenza:
Although some scientists are cautiously optimistic about the possibility of a mass immunisation program, provided that the vaccines are highly effective against the virus, others remain sceptical and caution against making unsubstantiated predictions about vaccine-induced herd immunity to Covid-19. Dr Alexander Stockdale, NIHR Academic clinical lecturer in clinical infection, microbiology and immunology at the university of Liverpool, stressed the need to resist jumping to conclusions in the absence of real world data:
The level of herd immunity necessary for COVID-19 control is unknown given that we haven’t got a vaccine with evaluable data and these estimates rest on a number of assumptions yet to be validated. I don’t think we could say as such there is scientific consensus at all as these are predictive models not actual data.
For example, the WHO has suggested a threshold of 50% disease risk reduction for approval of a candidate vaccine. There is a debate about whether disease reduction would translate to a reduction in transmission given that the type of immunity induced by vaccination may not be sterilising, i.e. it might reduce severe disease but not necessarily reduce transmission to the same degree.
Answering a related question on how effective a vaccine would need to be in order to halt the pandemic if it were administered to 70-80% of the population, Dr Stockdale said:
In general terms vaccine coverage must be higher if efficacy is lower. I cannot provide an estimate as there are still many unknowns here – the proof is in the pudding and evaluation of this must wait for the approval of a vaccine and publication of the phase 3 trial data! There may be surprises along the way and we may be in for a bumpy ride.
For example, issues of fair vaccine allocation, differential efficacy in different populations, the potential effect of rare but serious side effects on population uptake, the role of anti-science and anti-vaccination influence over time.Dr Alexander Stockdale, university of Liverpool, September 2020.
As reported in the Financial Times, with 300 potential vaccine candidates in the pipeline – 9 of which have already proceeded to phase 3 clinical trials – the flood of data helping humanity make sense of its latest invisible pathological enemy continues rushing down our digital waterways at breakneck pace.
According to Devi Sridhar, professor and chair of global public health at Edinburgh university medical school, based on other diseases which have plagued humanity throughout history, vaccine-induced herd immunity combined with other measures presents our best realistic hope of controlling and/or eradicating Covid-19. By contrast, since so-called natural herd immunity has never been achieved for many of these deadly pathogens, pursuing this latter, highly controversial approach looks likely to be a dangerously ineffective strategy against the novel Coronavirus:
1. This is assuming that the median herd immunity threshold for SARS, which based on these datasets is 65% (between 50-80%), is similar to SARS-Cov2.