IN a week in which the UK hit the grim milestone of 100,000 Covid deaths, vaccination has never felt more urgent.

If nearly everything else about the UK's response was sorely lacking - from disastrous lockdown delays to open borders - we have at least pulled ahead of the pack in the vaccines race. Only Israel and the United Arab Emirates are ahead.

The latest news on Novavax (the UK already has 60 million doses on order) is further cause for optimism.

HeraldScotland: More than one in 10 people in the UK have now had a first vaccine dose (Source: Our World in Data)More than one in 10 people in the UK have now had a first vaccine dose (Source: Our World in Data)

Clinical trials involving participants aged 18 to 84 show it is 89 per cent effective at preventing Covid illness, but crucially 86% effective against the highly transmissible UK strain and 60% effective against the South African variant.

Moreover, it is one of the most promising candidates when it comes to inducing sterilising immunity - that is, preventing infected people from transmitting the virus - after preclinical trials in non-human primates found that it virtually eradicated the pathogen from their respiratory tracts.

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Vaccines which can achieve this are seen as the Holy Grail of immunisation, as they can achieve herd immunity much more quickly, hastening the return to normality.

It remains to be seen whether these findings are replicated in humans, however, and - if approved by regulators - Novavax will not be rolled out until the second half of this year.

In the meantime, debate rages on over the pace and practicalities of Scotland's vaccine delivery as we near the target to finish inoculating the first wave of priority groups by Friday.

HeraldScotland: Vaccine coverage in Scotland continues to lag behind other parts of the UK (Source: Travelling Tabby)Vaccine coverage in Scotland continues to lag behind other parts of the UK (Source: Travelling Tabby)

To date, England has vaccinated 12.1% of its population with one dose compared to 9.4% in Scotland, including more than 90% of over-80s in the community against some 60% in Scotland.

But in care homes - where Covid mortality rates have been highest - Scotland has been consistently in front, with 95% of residents having had one dose by last weekend compared to 75% in England.

The next phase, as the immunisation programme works its way through the over-70s, over-65s, shielding patients, second doses, and then down through the over-60s and over-50s, will be a fairer gauge of the strengths and weaknesses of the Scotland's health board-led system.

One potential pitfall is the patchwork approach to delivery in Scotland. This may not slow things down, but it is liable to create some confusion among the general public.

For example, Sunday's announcement that 70-79-year-olds should look out for "blue envelopes" in the post was partially misleading (and not just because they were actually white).

Firstly, it turned out that in two of the six 'blue envelope' health boards - Lothian and Greater Glasgow and Clyde - most GPs have actually opted to vaccinate the over-75s and shielding patients on their practice lists themselves.

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As a result, a 75-year-old man living in Edinburgh will be invited to his GP surgery, while his 74-year-old wife receives a 'blue envelope' inviting her to attend one of the region's mass vaccination centres.

In comparison, in health boards such as Lanarkshire, Grampian, the Borders, and the Western Isles everyone aged 79 or younger will be vaccinated through these community hubs, while in Tayside and the Highlands GPs are immunising everyone over 65, plus the clinically extremely vulnerable, in their own practices.

HeraldScotland: The NHS Louisa Jordan is one of 16 mass vaccination sites in Greater Glasgow being used for under 75s The NHS Louisa Jordan is one of 16 mass vaccination sites in Greater Glasgow being used for under 75s

Already some teething problems have emerged. In some cases mass vaccination centres are further away and harder to reach for elderly patients than the GP surgery where no doubt many expected to be going.

Sites which are easy to reach if you are healthy and mobile, have a car, or a relative who can drive you, can be a hurdle for more deprived people who may have disabilities or health conditions such as heart disease that increase their risk from Covid.

READ MORE: Anger over winter flu vaccine 'shambles' that will see youngest vaccinated last 

The rollout of the winter flu programme already highlighted problems with vulnerable elderly people faced with catching multiple buses during a pandemic just to get to and from their vaccination clinic.

With GPs and health boards using separate IT systems, there are also reports of people in their 80s who have already been vaccinated once by their GP being mistakenly invited for a "first dose" by their health board.

Meanwhile, shortages of district nurses to vaccinate the housebound (unless GP practices have opted to do the immunisations themselves) are leading to cases of vulnerable people in their 90s feeling left behind and anxious, having heard nothing about their first jag at a time when those in their early 70s are receiving appointment letters.

HeraldScotland: Western Isles, with one of the oldest populations in Scotland, is vaccinating through community hubs (Source: Public Health Scotland)Western Isles, with one of the oldest populations in Scotland, is vaccinating through community hubs (Source: Public Health Scotland)

In areas such as Lothian and Greater Glasgow, it is also possible that people in their early 70s - who are receiving appointments now - will end up being vaccinated before those in their late 70s because GPs will be reluctant to send out invitations until they have vaccine supplies in their fridges.

There are plenty who say that England's system, where GPs manage the rollout in their own areas and do not have to go through convoluted health board ordering systems to obtain their vaccine, is more efficient.

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But it must be said that Scotland's system is the result of a contract (negotiated between the BMA and Scottish Government) which the vast majority of GPs voted for in 2018 - albeit for reasons that had nothing to do with any desire to give up responsibility for immunisations.

In fact, plenty were sceptical of this particular policy long before the pandemic.

The real incentive was the contract's new funding formula, which saw an uplift in income for most practices - particularly those in more affluent, urban suburbs.

The picture isn't perfect in England though. Coverage for the over-80s varies widely by council area and an analysis this week revealed much lower vaccination rates among black elderly than white, more deprived people, and those with severe mental illnesses or learning disabilities compared to other medical conditions.

Covid hit the poorest, sickest, and oldest hardest. However we roll out the vaccines, these are the groups who should be first in line.