Covid Scotland: Case rates lowest in unvaccinated as double-jabbed elderly drive rise in hospital admissions

It comes amid "weird" data showing that case rates have been lower in unvaccinated individuals than the single, double, or even triple-jabbed since Omicron became the dominant variant in Scotland, reports our sister title The Herald. 

The counterintuitive data from Public Health Scotland (PHS) contradicts previous pandemic trends which have consistently shown infection, hospitalisation and death rates to be highest among the unvaccinated.

However, one expert stressed that the patterns probably reflect factors such as Omicron initially transmitting in more affluent communities.

"It does appear weird until you start breaking things down," said Professor Rowland Kao, chair of veterinary epidemiology and data science at Edinburgh University.

Infection rates have been lowest since December 18 among the unvaccinated group, in a reverse of patterns seen previously in the pandemic

According to the latest PHS report, the Covid death rate has been consistently higher since December 4 in the double-jabbed compared to the unvaccinated - but much lower in the triple-jabbed.

The report defines a Covid death as "an individual who has tested positive by PCR for SARS-CoV-2 [the coronavirus which causes Covid] at any time point and has Covid-19 listed as an underlying or contributory cause of death on the death certificate".

In the final week of December, the death rate was 7.06 per 100,000 among the double-jabbed compared to 4.79 per 100,000 in the unvaccinated, and 0.21 per 100,000 in the triple-vaccinated.

In the week ending January 7, the hospitalisation rate was also twice as high in the double-jabbed compared to the unvaccinated - 130 admissions per 100,000 versus 59 per 100,000 - but fell to just 15 per 100,000 in the triple-jabbed.

The admissions data does not differentiate between patients in hospital 'because of' Covid and those who tested positive while being treated for other ailments, but PHS said the high hospitalisation rate for double-vaccinated individuals is being driven by increasing admissions among over-70s who are not yet boosted and whose immunity is waning.

It added: "In other age groups the rates remain lower for those with two doses compared to those with one dose or unvaccinated.

"This group of individuals aged 70-plus who have had two doses of vaccine but have not yet had a booster may include some very vulnerable individuals."

The hospitalisation was twice as high in the double-jabbed compared to the unvaccinated, but PHS said this was skewed by admissions in over-70s and was not being seen in younger age groups

The number of over-70s being admitted to hospital with Covid has surged from 131 in the week ending December 14 to 370 in the week ending January 4.

While uptake has been strong, around 38,500 adults over 70 in Scotland are still due boosters.

The report also shows that during the three weeks to January 7, Covid case rates were consistently lowest in the unvaccinated population.

Preliminary data for last week - which is age-standardised to adjust for the fact that younger people are more likely than older adults to be unvaccinated - shows a Covid case rate of 11 per 1000 in the unvaccinated group compared to 15 per 1000 for those who had received a booster or third dose, and 25 per 1000 for the double-vaccinated cohort.

People are defined as being triple-jabbed if they test positive for Covid more than 14 days after their booster, ruling out explanations such as people contracting the virus in crowded queues at vaccine hubs in the run up to Christmas.

Covid hospital admissions have been rising steeply in the over-70s

Prof Kao said Omicron was "evening out the playing field" in term of infections partly due to its ability break through vaccine protection, but also because had seeded through more affluent postcodes and arrived at a time when people previously protected by working-from-home were less likely to be doing so.

He said: "If you look at the initial spread of Omicron the deprivation relationship was inverted.

"You were actually more at risk of being exposed to Omicron if you lived in an area of lower deprivation, and if you're more affluent you are also more likely to have been double or triple vaccinated.

"It's not just in Scotland; a friend of mine in Wales is seeing exactly the same thing and saying 'what in the world is going on?'.

"My suspicion is that we have this initial explosion of infections which ignores all the previous rules, and that this question of 'where did it start off?' is more important that all the other risk factors."

Since early December, the death rate has been higher in the double-vaccinated than the unvaccinated, but this again is likely to reflect waning immunity in hospitalised and vulnerable over-70s who were not yet boosted

In addition, Prof Kao said it was unclear how well immunity from multiple prior Covid infections protected against Omicron.

He said: "We know you get more protection from three hits of any sort - that could be two doses plus infection, two doses plus a booster.

"But we don't actually know what would happen if you got infected two or three times, and there are probably people out there who have been.

"You have these pockets of deprived areas in particular where the virus has been circulating at a much higher rate."

A spokesperson for PHS said the figures could also be skewed by factors such as higher testing uptake by "more health conscious" vaccinated people, adding that "these biases become more evident as more people are vaccinated and the differences between the vaccinated and unvaccinated population become systematically different".

Cases and hospital admissions both now look to be in decline in Scotland

She added that the higher case rates in the double-vaccinated are being driven by infections among over-40s whose immunity is waning, but who have not yet taken up or become eligible for boosters.

She added: "The vaccination status of cases, inpatients and deaths should not be used to assess vaccine effectiveness because of differences in risk, behaviour and testing in the vaccinated and unvaccinated populations."