Media of all types are full of people telling us the mistakes they think have been made in controlling Covid-19 in New Zealand, and how much better we could have done – if they had been in charge.
Judging by their lack of understanding of the subject, we should be very glad they are not in charge.
Unlike DNA viruses, RNA viruses such as influenza and coronaviruses evolve very rapidly, and it is more important to adjust quickly to a moving target than to falsely expect to be able to "get it right".
The United States has just reached 900,000 deaths attributed to Covid-19, and more than 76 million cases.
So far, 75 per cent of people in the US have received at least one dose of vaccine. For the whole world, there have been 5.7 million deaths and 391 million cases reported, with 61 per cent of people having received at least one dose of vaccine.
New Zealand has had 53 deaths and 17,546 cases at February 4, with 95 per cent of people having received one or more doses of vaccine.
The New Zealand data is very accurate, because of the scale of our testing and data gathering activities.
The data for the rest of the world is a substantial under-estimate, due to under-counting of both cases and deaths.
Epidemiologists use a number of different methods for getting more valid estimates of disease occurrence and deaths, and the effects of diseases on the community. A standard method is to estimate excess mortality – how many more people are estimated to have died during the pandemic than would have been predicted to die, based on the recent past, but using powerful statistical procedures to adjust for complexities in the data.
A recent estimate gives excess mortality for the world attributable to Covid-19 of 20.6 million and, for the US, 1.2 million. Almost four times as many people have died of Covid-19 worldwide as the official figures suggest.
In New Zealand, at least 2300 fewer people have died than expected "under normal circumstances" over the course of the pandemic.
Because of the public health measures applied and the high degree of compliance with the measures, deaths from other causes have declined. We have saved lives rather than lost them.
Another way of looking at this is to consider life expectancy – at what age do we expect the "typical person" to die? This is more complicated to calculate and can only be determined retrospectively.
Over recent decades life expectancy in New Zealand and around the world has been rising steadily due to improved health of the population. But in a recent study that evaluated 37 countries, life expectancy in the US and Russia fell by two years between 2018 and 2020, due to the effects of the Covid pandemic.
In 30 other countries life expectancy also fell, but by smaller amounts, and three countries had no change. Only two countries had an increase in life expectancy over that period - New Zealand gained eight months and Taiwan four months.
In total, more than 28 million years of life were lost in the 32 adversely affected countries in 2020, attributable to the pandemic, but life years increased in New Zealand.
That is in addition to 10,000+ deaths averted because we went hard, and few cases of "long Covid", in which people suffer long-term ill-health.
Despite doomsayers claiming that the control measures applied by New Zealand would be very damaging to the economy, it has in fact rebounded from the initial global impact of the pandemic far better than countries that adopted less intensive measures, and has achieved high growth in real GDP and the lowest unemployment rate ever recorded in the country.
So New Zealand has managed to achieve both an outstanding result in saving the community from many thousands of deaths from Covid that would have occurred if a relaxed approach had been adopted as proposed by critics and commentators throughout the pandemic, and economic performance through the pandemic has been very favourable, under difficult circumstances.
• Professor Roger Morris is an epidemiologist and economist who has contributed to disease control in more than 50 countries, and has trained epidemiologists in Africa and across Asia how to respond to emerging diseases.