France's public health measures in response to SARS-CoV-2 B.1.1.7 variant

By Marzia KhanJun 7 2021

While the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic led to most European countries going into lockdown in March 2020 to slow the spread of the disease, the virus continued to impact countries such as France through the end of summer 2020. A new lockdown was also established by France from 29^th October to 28^th November, followed by 6 pm curfews and the introduction of COVID-19 vaccinations in 2021.

The emergence of a new SARS-CoV-2 variant in the UK, B.1.1.7 (GR/20I/501Y.V1), in October 2020 caused a spread into other European countries, including France, from December 2020.

This novel variant was suggested by recent studies to be more transmissible than the original virus, by up to 70%, causing an impact on infection rates and virus dynamics in specific areas.

A study undertaken by the Toulouse Institute for Infectious and Inflammatory Disease (INFINITy) in France evaluated the impact of the SARS-CoV-2 variant B.1.1.7 in France with higher positive tests found, as well as analyzing the result of health measures such as social distancing and vaccinations. The research is published in the journal Viruses.

Statistical Models

Early prediction models based their estimates on published positive cases of the virus, however they ignored the patients' ages or a diffusion coefficient that takes into account the evolution of the disease. This also seemed to be the case for the Johns Hopkins University predictive model, which underestimated the effect and spread of SARS-CoV-2 in Italy and overestimated the spread in France and the UK.

The model used in this study consists of a version of a susceptible-infectious-recovered (SIR) model, which can be seen as being more suitable for analyzing the spread of the virus in different populations.

In this model, diffusion/transmission coefficients vary with probability of infection as well as reduction coefficients that take into account public health measures that may influence virus transmission.

The circulating forms of SARS-CoV-2 on Toulouse urban area during January 2021 and early February. (A): week 1 (46 samples), (B): week 2 (141 samples), (C): week 3 (181 samples), (D): week 4 (216 samples), (E): week 5 (110 samples).

Findings

The parameters of the model used by the French scientists who investigated the spread of the SARS-CoV-2 virus included public health measures such as social distancing and curfews, as well as mass testing and the introduction of vaccinations.

The time period which was assessed was the time after the positive test peak from 14^th February to 1^st March 2021.

The results consisted of a decrease in the positive tests from the peak on 13^th February to 9.8% on 1^st March 2021. However, when thinking about whether to decrease the public health measures, predictive models have suggested that halving the testing capacity would contribute to the increase of the virus, increasing positive tests to 11.2% on 1^st March (seen in Figure 1). In addition, the halting of mass testing will result in the virus spreading by 12.6%.

The study predicted that the lifting of all measures on 14^th February 2021, with the mass testing and vaccinations still being in place, would increase the infection rates to 59% in March 2021.

The study concluded that public measures such as social distancing, curfews as well as mass testing, and the introduction of vaccinations enabled the UK variant B.1.1.7 to be controlled more readily.

This variant quickly became a major circulating strain with it accounting for 60% of the cases found in the Toulouse urban area in February.

This was a definite variant of concern in France, and so these measures enabled it to be controlled in populated areas as the variant currently is accountable for more than 90% of positive tests.

Maintaining these measures will allow for further prevention and control of SARS-CoV-2 over time, as well as a decline in positive tests.