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The race between vaccinations and variants in the US and Germany
By David Mackie
Click here for the full Note and disclaimers
Our recent analysis has discussed how long it would take for the US and Germany to reach the “new normal” given the rapid spread of the Delta variant 1. That destination is in sight in both countries and should be reached in six to eight weeks. However, it is also important to consider what happens to the effective reproduction number along this journey, and this is what we do in this note.
Whether or not the US and Germany experience another wave of COVID-19 infections over the coming weeks depends on the evolution of the effective reproduction number. Since late April, the effective reproduction numbers in both the US and Germany have been below one, so new infections have been falling. Looking ahead, the Delta variant will be putting upward pressure on the effective reproduction number, while vaccinations will be putting downward pressure. There is therefore something of a race between the variant and the vaccinations. Also important is the starting level of the effective reproduction number. If the effective reproduction number increases, pushed up by the spread of the Delta variant without full mitigation from vaccinations, but it remains below one, then new infections will continue to fall. This is likely to be the situation in Germany, because the current level of the effective reproduction number is so low, at 0.63, and the pace of vaccination is so high. Alternatively, if the spread of the Delta variant pushes the effective reproduction number above one, then new infections will rise. This is likely to be the situation in the US, because the current level of the reproduction number is only just below one, at 0.90, and the pace of vaccination is slower relative to the size of the population.
Tables 1 and 2 describe a number of scenarios showing where the effective reproduction number will be when the Delta variant reaches full prevalence, given different assumptions about the speed at which the variant spreads and the pace of second vaccinations. The scenarios show clearly that the situation regarding another wave of infection improves as the spread of the variant slows down and as the pace of vaccination increases.
The situation in Germany looks good. We assume 10% prevalence of the Delta variant in Germany currently and on the basis of the UK’s experience it might be expected to become fully prevalent in 42 days (six weeks). Currently, the pace of second vaccinations in Germany is 560,000 a day. Our calculations suggest that only if the variant spreads relatively quickly, and the pace of vaccination slows, will the effective reproduction number go above one. Otherwise, it will remain below one, preventing another wave of infection (Table 1).
The situation doesn’t look so good in the US. We assume 30% prevalence of the Delta variant in the US currently and on the basis of the UK’s experience it might be expected to become fully prevalent in 35 days (five weeks). Currently, the pace of second vaccinations in the US is 880,660 a day. Our calculations suggest that the US will have another wave of infection, unless the spread of the variant is relatively slow and the pace of vaccination picks up sharply (Table 2).
Despite the likelihood of another wave of infection in the US, the macro consequences are likely to be limited. Although the basic reproduction number for the Delta variant is much higher than for other strains, which means more infections, the hospitalization and case fatality rates look to be much lower (Table 3). In an examination of all sequenced cases since February 1, Public Health England have shown that the hospitalization rate for the Delta variant is less than half of the hospitalization rate for the Alpha variant, while the case fatality rate for the Delta variant is around a tenth of that for the Alpha variant 2. But, of course, even with lower hospitalization and fatality rates, the pressure on the health care system and the absolute number of deaths will go up if there is a big surge in infections, as happened earlier this year in India. Avoiding this situation is what prompted the UK government last week to delay the final step of the lockdown easing by four weeks.
Table 1: German reproduction number when the Delta variant reaches full prevalence
| Speed of spread of variant, days to full prevalence
| Pace of second doses/day
| 350,000
| 450,000
| 560,000
| 35
| 1.17
| 1.00
| 0.81
| 42
| 1.05
| 0.85
| 0.62
| 49
| 0.94
| 0.69
| 0.43
| Source: J.P. Morgan
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Table 2: U.S. reproduction number when the Delta variant reaches full prevalence
| Speed of spread of variant, days to full prevalence
| Pace of second doses/day
| 880,000
| 1,000,000
| 1,500,000
| 28
| 1.47
| 1.44
| 1.27
| 35
| 1.40
| 1.35
| 1.14
| 42
| 1.33
| 1.27
| 1.01
| Source: J.P. Morgan
| | | | |
Table 3: The impact of the Delta variant compared to the Alpha variant in England
| All sequenced cases from 1 February to 14 June
| Variant
| Case numbers
| Hospital admissions
| Hospitalization rate, %
| Deaths
| Case fatality rate %
| Alpha
| 148,513
| 4447
| 3.0
| 1614
| 1.1
| Delta
| 60,624
| 806
| 1.3
| 73
| 0.1
| Source: J.P.Morgan. Public Health England.
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1 The “new normal” is defined as the situation where mobility has returned to pre-pandemic levels, current NPIs remain in place and the Delta variant is fully prevalent. Reaching the “new normal” requires around 60% of the total population to be fully vaccinated.2 Public Health England, SARS-CoV-2 variants of concern and variants under investigation in England, Technical Briefing 16, June 18, 2021 |
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