The UK government announced yesterday that it was planning to lift all remining legal restrictions to prevent Covid-19 transmission. Other Western countries are acting likewise despite the current wave of Omicron infections. Does reducing legally enforceable mitigation actions make sense?
What are the current data?
- As mentioned previously in this blog, the UK’s weekly PCR sampling of a large random population provides the best data on the underlying trends in the numbers of new cases
- These data are very clear: for the past several weeks, the underlying rate of infection is consistently around 5%
- The most recent data on 9th February showed that 1 in 19 of the English population were infected last week.
- The rate varies by age and is around 1 in 8 for children but still 1 in 40 for those over 70
- Indeed, in Scotland and Northern Ireland these rates are increasing slightly
- Hospitalisations in England have dropped by 25% in the past one month
- But as reported, hospital data are challenging as they do not discriminate between being in hospital with Covid-19 as opposed to because of Covid-19.
- Thus, assuming the average age of all patients in hospital for any reason is around 70, then by chance alone 1 in 40 will be positive for Covid-19.
What is clear about Omicron?
- The following are well known but worth repeating
- Omicron is responsible for the overwhelming proportion of cases currently
- Omicron is much more transmissible than any other variants, frequently before people test positive, and in both symptomatic and asymptomatic people
- In the overwhelming majority of cases, Omicron is self-limiting illness lasting from a few days to 2 weeks. Although robust data from non-Covid-19 viral infections are not available to allow statistical comparisons, the clinical impact of Omicron for most affected individuals is broadly similar to that from seasonal flu
Have vaccines altered the equation?
- Again, much of the information below is well known
- Three doses (but not 2) provide as good a protection against serious Covid-19 that could be reasonably expected from vaccines for any similar infection
- Current vaccines do not, however, prevent people getting a mild to moderate illness with Omicron
- Current vaccines do not prevent reinfection in people who were infected, even in the recent past, with Delta
- Although it is likely that vaccines have been in large part responsible for the lower risk with Omicron of severe infection, unvaccinated or inadequately vaccinated people are less likely to become seriously ill following Omicron than they were with Delta
What don’t we know about Omicron?
- This variant has only been around for 2 months so that limits what we know
- It is thus too early to know what the risk of reinfection with Omicron is (official data require a minimum of 90 days to prove reinfection)
- There are no data yet on the decline in natural immunity following Omicron which would push up the risk of reinfection
- Data would suggest that there is a waning of immunity following 3 doses of vaccine against getting ill, but too little data to know if the protection against serious infection is longer lasting
- We also don’t know what the risk and severity is of ‘long CoVid’ following Omicron. Both might be lower than following Delta, but that does not mean that long Covid-19 might not be a significant problem for many
And in addition, we don’t know:
- Given the very high rates of infection in the population, will the point be reached that so many will have had natural infection that there is the long sought-after herd immunity?
- There is absolutely no sign of that happening and Omicron does not look like it is going to disappear
- Could Omicron be replaced by a more severe variant?
- No-one could be absolutely sure that this could not happen
- There will be new mutations and some may have the double whammy of being both more transmissible and more severe
- In evolutionary terms, Omicron has been very successful in infecting large numbers – in part because it only causes a mild illness – so there is no ‘benefit’ in its mutating to a riskier variant
Putting it altogether!
- The aim of legal restrictions is to add to personal behaviours to reduce the risk of transmission
- My first question is whether there is a continuing public health need for legal restrictions to reduce transmission
- Omicron is an infection that is (i) predominantly mild and (ii) for which vaccines have achieved their goal of minimising hospitalisations?
- There are economic, social and educational costs from any legal restrictions, so they are not a ‘zero sum game’
- At the very least the case that there is a current public health need is far from compelling
- My second question is whether the extant legal restrictions achieve their goal – ie do they do anything useful?
- Transmission is at its highest ever and not decreasing
- (Anecdotally I am more aware of friends and family getting ill than at any time during the pandemic)
- It could be argued that the problem is non-adherence to the restrictions
- Alternatively, the restrictions actually do very little to control infection rates where most transmission occurs too early and silently
- Either way, the case for retaining restrictions that don’t work in practice, independent of any need, is also far from compelling
- Of course, politicians do not always make such decisions on scientific grounds but in this instance lifting of restrictions is defensible
- It is also challenging to maintain messaging about desirable behaviours such as mask wearing and hand washing in the teeth of major changes in government policy
- Lifting the quarantine therefore would not stop me making a personal choice to continue to wear a mask on public transport
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