Today, Scotland will take its first small (official) steps out of lockdown.

Informally, of course, some already appear to have been pushing the boundaries if statistics on increased car and public transport use and scenes of crowded parks and beaches on recent sunny days are anything to go by.

Tomorrow marks exactly 10 weeks since pubs, restaurants, cinemas and leisure venues across the UK were forced to close, and nearly as long since the public were ordered to stay at home "except for essential purposes".

The restrictions were a sharp pivot away from a flu-based strategy of herd immunity (after scientific advisors projected this would claim up to 500,000 lives in a worst case scenario of a 1% mortality rate) in favour of severely curbing exposure to the virus.

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Given that the UK’s death rate from Covid currently ranks third highest in the world behind Belgium and Spain (555 deaths per million compared to 574 per million in Spain and 815 per million in Belgium), it is hardly a success story.

Yes, by cutting all other routine elective procedures and a substantial portion of urgent work from the NHS, we did succeed in preventing it from being overwhelmed. But at what cost to non-Covid patients remains to be seen.

One area of growing interest among countries emerging from lockdown is what impact the strategy has had on the prevalence of Covid-19 antibodies within the population - and how much this might matter in the weeks and months ahead.

Reactions to initial results have ranged from surprise to alarm.

Despite Spain’s huge death toll, preliminary results from antibody surveillance using blood samples from 36,000 randomly selected households nationwide indicated that just five per cent of the country’s population had been infected with the virus so far. Even in Madrid, which was hit hardest, it averaged just 11%.

This is worrying on two fronts: it means the vast majority of its 47 million people remain susceptible, and it puts the mortality rate from the virus at just over 1% - the upper end of what was originally predicted.

Researchers at Paris’ Pasteur Institute have similarly estimated the antibody prevalence in France to be around 4.4%, despite having the world’s fifth highest Covid death rate per head.

The study, published in the journal Science, notes that “around 65% of the population should be immune if we want to control the pandemic by the sole means of immunity”, adding that current antibody prevalence was “insufficient to avoid a second wave if all control measures are released at the end of the lockdown”.

Italy began rolling out its own antibody surveillance drive on Monday, with a goal to collect 150,000 blood samples from a representative sample of the population across 2000 sites.

A much smaller study in the UK - using just 1000 participants - indicated similar levels of immunity, projecting that 5% of the UK population had already been exposed to the virus, rising to 17% in London.

In the US, blood samples suggest 21% of people living in the city of New York have Covid antibodies.

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In Scotland, we are now three weeks into a randomised antibody surveillance project using blood samples collected from various health boards and analysed centrally in Inverness. No results have yet been disclosed, however.

Optimists have argued that the low levels of Covid antibodies in the population are testament to the success of lockdown itself in severely curbing population exposure.

But this is challenged by puzzling results from Sweden, where just 7.3% of Stockholm’s inhabitants were found to have developed Covid-19 antibodies by the end of April despite its light-touch approach to social distancing.

Swedish public health officials had expected around 25% of the population to be carrying Covid antibodies by May 1, rising to 40-60% by mid-June.

The Swedish government insists it is not pursuing a strategy of herd immunity per se, but rather attempting to balance a goal of just enough exposure to limit the risk from a second wave with just enough restrictions to slow the spread of the virus and avoid its health service becoming swamped.

It partially closed schools, banned gatherings of more than 50, encouraged home working and asked the elderly or ill to stay at home. Shops, restaurants and gyms remained open, however.

Of course, it remains unclear to what extent - and for how long - Covid antibodies actually protect against re-infection from the virus, a potential complication for scientists trying to develop an effective vaccine.

A Dutch study of four viruses from the same coronavirus family, published this week but spanning a 35-year period, found a “substantial reduction” in antibodies six months after infection and “frequent re-infection” after 12 months.

If antibody prevalence really is as low as these studies suggest - and not even recovery from infection can shield us anyway - the road back to normality could be very long indeed.