Examining the difference in 1st and 2nd wave COVID-19 deaths

There are three key differences between the first and second wave that likely impacted on COVID-19 deaths in England: The second wave was worse (more infections, hospitalisations, and deaths) than the first wave; our collective understanding of COVID-19 was greater in the second wave, meaning we had a better idea of how best to treat severely ill patients; and the second wave coincided in part with the UK’s vaccine rollout.

These three reasons, combined with the potential difference in individuals’ behaviour in the two waves, means that a direct comparison of deaths in the two waves is not possible. It is also not possible to easily isolate these three reasons and assess their relative effects.

One possible way that offers some insight is to examine the difference in deaths in different age-groups between the first and second wave. We can examine how deaths declined from their first and second wave peaks for different age groups. For example, the deadliest week in the first wave sadly saw 2760 deaths for those aged 80+ in England. In the following week, deaths in those aged 80+ had declined by 12% to 2418, in the week after that they had declined by 35% relative to the peak to 1785, etc. This can then be compared to how deaths declined for those aged 80+ in the weeks following the second wave peak. (Note that the difference between two percentages is known as a ‘percentage point’ (%-pt) i.e. the difference between 5% and 10% is not 5%, but 5%-pts, as going from 5% to 10% represents a 100 percent increase (as it is doubled)).

The following graph illustrates this percentage point difference between the decline in second wave and first wave deaths relative to their peaks. A positive value means that deaths for that age-group declined faster in the first wave than the second wave, whilst a negative value means that deaths for that age-group decline faster in the second wave than the first wave.

Source: NHS England

In the six weeks following the first and second waves’ peaks in deaths, deaths declined relatively faster in the first wave for those aged 40-79, but declined relatively faster in the second wave for those aged 80+. From the seventh week onwards, deaths have declined faster in the second wave for those aged 60+, but faster in the first wave for those aged 40-59.

This would suggest that the vaccine rollout has acted to reduce deaths in the older age-groups, as 10 weeks after the second wave peak, deaths declined relative faster for those aged 60+ compared to the 10 weeks after the first wave peak, but relatively slower for those aged 40-59, when compared to 10 weeks after the first wave peak. Indeed, this is consistent with a recent analysis by Public Health England (see here) that found that, in data up to the end of March 2021, COVID-19 vaccine had prevented 10,400 deaths in those aged 60 and above.

Whilst this suggestion is encouraging, it is important to note that the analysis in this blog cannot say for certain how many deaths have been reduced due to the COVID-19 vaccine programme. Nevertheless, it is relatively certain that the vaccine programme is acting to prevent COVID-19 deaths, and it is likely that the quicker decline in deaths in older age-groups in the second wave, relative to the first wave, is at least in part due to the COVID-19 vaccine rollout.

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