As the coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to distress worldwide, new variants are emerging that threaten the possibility of containment by current vaccines or therapeutic antibodies.
This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources
Variants of concern may drive higher transmission
These, called the variants of concern (VOCs), have been called the UK, Brazilian, and South African variants, depending on where they were first identified.
Now, a new preprint research paper posted to the medRxiv* server reports the estimated effects of these variants on epidemiological parameters of virus spread, including the seven-day incidence rate.
The designation VOC comes from the fact that they have been associated, on epidemiological grounds, with higher transmissibility based on earlier strains.
The countries and regions that first reported these VOCs' emergence saw a simultaneous increase in infections towards the end of 2020 and early 2021. This increase occurred despite the high levels of social distancing that were practiced at that time. There was an estimated increase by 50% to 70% in the risk of infection with the UK variant.
Some preliminary findings have also shown that mortality rates are rising in the UK. Moreover, epidemiologists know that when novel variants spread rapidly at a local level, they are sure to increase international transmission rates as well.
VOCs in Germany
All three VOCs were identified in Germany by the middle of January 2021, having been imported via returning travelers from countries where these were spreading to a large extent. The researchers sought to identify any link between VOC cases and infection rates.
Temporal and spatial distribution of VOC cases in Germany. Panel A counts NUTS-3 regions with confirmed VOC cases over time. Panel B reveals that the 7-day incidence rate (by day of reporting) decreases for Germany and Schleswig- Holstein but increases in Flensburg (a region with many confirmed VOC cases). Panel C shows the spatial spread of VOC cases by February 4, 2021. Flensburg and Cologne, Düren and Leverkusen report most confirmed VOC cases.
The seven-day incidence rate refers to the number of new infections over the last seven days reported per 1,00,000 people. The VOC data was obtained from a database that acquires information on confirmed cases of these three VOCs, based on newspapers and public health documents. The data was crosschecked against aggregated data from the premier disease control institute in Germany, the Robert Koch Institute (RKI).
The researchers found that in over half of the ~400 NUTS-3 regions, one or more VOC infection cases had been documented by the beginning of February. The number of such regions experienced exponential growth by the end of January. Among these, Flensburg and three localities in the North-Rhine Westphalia (NRW) region were among the top 5% affected regions.
Local infection rates driven by VOCs
The investigators aggregated VOC infections with daily infection rates for each NUTS-3 region and calculated VOCs' effects on the latter.
In Flensburg, a city of 90,000 residents, the infection rates were constantly below Germany's average in 2020. However, in January 2021, the seven-day incidence showed a steep rise. The main driver was parties on New Year's Eve in infringement of lockdown regulations.
In Flensburg, the seven-day incidence rates went up threefold within 20 days of January 5, 2021, the study group's start date. This was thought to be due to the potential superspreading events at the illegal parties on New Year's Eve.
Among several infections traced to these parties and some unrelated to them, the UK variant was first identified on January 24, 2021. Within ten days, the number of VOC infections had ballooned to almost 150.
In the NRW cluster of cities, the increase was about 40%, after 20 days from the start date. This is more in keeping with earlier results.
Comparison of regions with VOCs
In all regions with one or more VOC, the incidence rate went up by 15/1,00,000. This is comparable to other regions. Suppose the sample includes those where the VOC was confirmed before January 22, or where nine or more cases have been reported. In that case, the incidence rate is found to be 37% higher on average, corresponding to 40 more cases per 1,00,000 compared to the 109/1,00,000 in the comparison regions.
The effect size is smaller if this period is extended by one, two, or three weeks. This suggests that infection rates change around the time when the VOC is documented.
Panel event study
When measured 20 days after the start of the treatment period, the seven-day incidence rate is found to be almost twice as high as before this period. The most extensive changes occur in the regions where there were nine or more VOC cases, and smaller changes are seen in those regions where the VOC emerged before January 22.
The explanation may be that the containment strategies that allowed the first few VOC infections imported from outside to be isolated failed as time passed.
What are the implications?
The researchers point out that the earliest date of VOC reporting in a region is just that and should not be taken to represent the variant's actual time of arrival. The rates of specific VOC testing are lower in Germany than international rates, leaving room for many unrecognized VOC infections.
The association between confirmed VOC cases and seven-day incidence rates does not directly show whether VOCs are actually more infectious than the older variants. Finally, testing rates may be higher in regions where VOC infections have been reported, which may itself lead to a spike in incidence rates compared to other regions.
The study shows that the emergence of a VOC drives up infection rates by 10-40%. When regions with high VOC counts are considered separately, the incidence may double or triple the rates at local level, in regions without reported VOCs.
The considerable rise in estimated infections is disturbing since VOCs may still make up only about 6% in the week between January 22 and January 29, 2021. With this low level of VOC infections in many regions, there is a possibility that the estimates are falsely low.
This can be corrected only by providing information on the spread of these variants. "We hope that our early assessment can fill the eminent knowledge gap regarding the epidemiological effects of VOC and inform health policy authorities about the need for swift actions to control local transmission."
This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources
Article Revisions
- Apr 5 2023 - The preprint preliminary research paper that this article was based upon was accepted for publication in a peer-reviewed Scientific Journal. This article was edited accordingly to include a link to the final peer-reviewed paper, now shown in the sources section.
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