LOWER exposure to the virus earlier in the pandemic could explain why Scotland now has the highest Covid infection rates in the UK, Scotland's chief medical officer has said.

Dr Gregor Smith said vaccinations were now "topping up" immunity levels among Scotland's population, but there are still large numbers of people with no antibody protection.

The latest national comparisons published by Public Health England show that Scotland's Covid infection rate is 26 per cent higher than England and the highest in the UK, at 69.4 per 100,000.

That compares to 37.8 in Wales; 56.7 in Northern Ireland; and 54.9 in England.

The figures, published yesterday, are based on the seven-day average up to March 26 to account for the time it takes to process specimens.

READ MORE: Scotland has highest virus rate in UK amid spike in cases among young

Previous surveillance, based on blood samples, estimated that around 22% of people in Scotland had developed Covid antibodies - either as a result of vaccination or prior infection.

That compared to nearly 35% in England, and around 30% in Wales and Northern Ireland, where virus rates had been higher.

Asked about Scotland's current higher infection rates during an online Covid briefing today, Dr Smith said: "One of the reasons for that could be that we've had lower virus rates previously, which means we've been less exposed than other parts of the UK - especially during the second wave before Christmas.

"So we probably have less natural immunity. Vaccination is topping that up, but we've got a bit to go to catch up with the other parts of the UK."

Professor Jason Leitch, Scotland's national clinical director, added that the situation should also "be a warning to us not to go too fast".

HeraldScotland: Scotland has had the highest case rate in UK for around three weeks (Source: Travelling Tabby) Scotland has had the highest case rate in UK for around three weeks (Source: Travelling Tabby)

"The way to get out of this is by going slowly and with vaccinations," added Prof Leitch.

However, there are signs that coronavirus cases - which plateaued during March - are beginning to fall again.

HeraldScotland: Cases are falling, although more slowly than they were in February Cases are falling, although more slowly than they were in February

In the seven days to April 1, a total of 3,233 positive cases have been detected - down from 3,862 in the week to March 25, and 4,107 in the week to March 18 - a decline of 21% over the past two weeks.

The average test positivity rate over the past seven days - at 2.4% - is also the lowest since the week ending September 23.

READ MORE: 400 Covid cases confirmed in Scotland in daily update

Overall, rates of Covid in Scotland and the UK as a whole are substantially lower than mainland Europe, which is now in the grip of an escalating third wave.

The clinicians also said they are not aware that there has been any significant a drop-off in attendance rates at vaccination centres.

It comes after some GPs said they were seeing a rise in no-shows for vaccine appointments.

Dr Punam Krishan, a Glasgow-based GP and broadcaster, tweeted on Wednesday: "Lots of people are not turning up to their vaccine appointments - this is not ok!

"The vaccines are precious and with many desperately awaiting their turn, please think twice before missing yours. Phone to cancel so we can offer it to someone else. Let’s not waste any more vaccines."

It comes as second doses are being rolled out and the push is on to complete everyone over 50, and younger people with health conditions, before the mid-April target.

There has also been increased scrutiny of the AstraZeneca vaccine - that main jag being used in the UK immunisation programme - after Germany this week banned the vaccine for patients under 60, and Canada for the under-55s, amid fears that it increases the risk of rare blood clots - especially among women.

France already limits its use to over 55s.

READ MORE: 'No evidence' to support restricting vaccine to older age groups

Dr Smith said: "We keep an eye on attendance rates at all our vaccination centres just to see whether there are any particular difficulties either because people aren't receiving appointments or because there may be a tailing off in people attending.

"We're pleasantly surprised, right from the beginning of the vaccination campaign, just at the high proportion of people who are taking up the offer of vaccination.

"We're not getting any strong signals at this stage that there's any change or hesitancy in people coming forward for the vaccine. But it's something we'll monitor."

Prof Leitch said some people were missing appointments because they received letters at comparatively short notice.

He said: "There are some who don't turn up partly as a result of the just-in-time appointments system, we have to do it fairly close to the wire, but if you miss your appointment we will give you another one. It's not one strike and you're out."