Scientists must long to travel back two years and revisit their Covid predictions. So too must commentators who relied on them. That March of 2020 was a nightmare month for the great game of prediction. Boris Johnson’s press conference on 3 March was a cautious occasion. He had just received wild reports from Whitehall’s scaremongers declaring that 80% of the nation “could be” about to suffer from a killer disease from which half a million “could die”. His response was to take comfort from his in-house scientists, guided down the path to “herd immunity” by his senior advisers, including Patrick Vallance. Daily briefings and hysteria mounted until 23 March, when Johnson performed the agony of volte-face. His capitulation to extreme lockdown was so abject as to make it hard for anyone who had followed his argument so far to agree with him. Most commentators cynically switched sides and said he should have capitulated sooner. My thinking was that we had been through this crying-wolf routine so often in the past, including from the modellers of Imperial College and perhaps their lobbyist friends in big pharma. Back in 1997 we had heard that millions “might die” from bird flu, and from Sars in 2003, and from swine flu in 2009. The scientists extracted vast sums from the government, including £560m on bird flu and swine flu vaccines that just sat unused in a warehouse. Imperial College was now terrifying Johnson with its much favoured “worst-case scenario” of half a million deaths if he refused total lockdown, irrespective of cost. A reasonable person might have reacted as I did. There was nothing to suggest that this epidemic was not another of the same. The wolves of big science were after headlines and money, and should be taken with a pinch of salt. Surely, I wrote, “come the spring, the crisis will have passed” – and spring was just a fortnight away. As the month progressed, though, Covid was clearly gripping the globe, from Asia to Italy, Spain, Germany and Poland. By early April the country was in deep lockdown and Covid was sufficiently virulent for me to admit: “I was wrong, or think I was.” Clearly this was not another Sars. But I stuck to my belief that it would end soon. I was comforted by the policy adopted by Sweden’s health chief, Anders Tegnell, who was rejecting lockdown, pursuing voluntary social distancing and relying on herd immunity rather than the draconian test-trace-and-isolate of regimes in China and Taiwan. As summer progressed, we assumed Covid was all over and that we would learn which responses were most effective. We learned nothing. Stringent lockdowns in China, Italy, New Zealand, Denmark and Britain had delivered both the highest and the lowest deaths per million. Tight test-and-trace had worked in South Korea, but so had its absence in Sweden. The latter suffered a bad outbreak in its care homes but still fared better overall than the UK and Spain Such comparison was wiped from the table by two dramatic events at the end of 2020. One was the emergence of a virulent second wave of Covid – and then a third. The other was the development and speedy production of vaccines. The gods of test-and-trace were toppled overnight by those of jab and booster. The unpredicted nature of both events dissolved much argument. Vaccination changed the terms of the debate. In Britain, it got Johnson off his volte-face hook. From spring 2021, Covid pessimism gave way to optimism in what was one of the great coups for modern science. But to those struggling to follow the argument, vaccination had a masking effect. If vaccination was so successful, why still lockdown? Should lockdown go the way of test-and-trace, a hoary old cure to be consigned to the museum? And what of mutations such as Omicron? Were they to be handled through vaccines and medicines, like flu, or to be treated as yet another evolving pandemic, to be met with the full force of resumed lockdown? The simple conclusion from the past two years is that it is still too early to say. We must await the mother of all public inquiries. The trouble is that the emerging statistics may offer little guidance. The government’s chief statistician, Ed Humpherson, recently told MPs to treat excess deaths as the most robust measure of the international comparison. They represented the ultimate impact of the pandemic on a nation’s health and longevity. But here we encounter yet more fog. The US Institute for Health Metrics and Evaluation reports extraordinary similarities between the impacts of Covid on, for instance, the UK, France and Germany. They had differing lockdown practices but near-identical excess death rates, roughly halfway down the global league table. Some of the lowest rates were in locked-down Finland but also in unlocked-down Sweden, which was half Britain’s rate. This suggests that the argument is by no means over. It may yet be that Covid deaths had less to do with lockdown and more with the overall efficiency of health services in confronting serious cases and in dealing with other deaths at the same time. The evidence may suggest that what was critical was the behaviour of different economic and social cultures in responding to lockdown. Sweden’s GDP declined in that critical year of 2020 by just 2.9%. Britain crippled itself with a decline of 9.4%. Is that perhaps why more Britons died? But this brings me uncomfortably close to wondering if I should have stuck to my original guns. Simon Jenkins is a Guardian columnist