Health

Can barrier gestures be relaxed without causing a COVID-19 resurgence in France?

To date, the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causal agent of the coronavirus disease 2019 (COVID-19) pandemic, has claimed more than 4.5 million lives worldwide. Globally, scientists have devised various strategies to contain the pandemic, such as vaccines, therapeutics, and various non-pharmaceutical measures. The non-pharmaceutical measures include lockdowns, curfews, and barrier gestures like social distancing and mask-wearing.

Study: Barrier gesture relaxation during vaccination campaign in France: modelling impact of waning immunity. Image Credit: Maria Vonotna/ Shutterstock

What is the duration of immune protection conferred by COVID-19 infection and vaccination?

Many studies use compartmental models to evaluate varied parameters of epidemic dynamics and assess the impact of social distancing and the approved vaccines in a given population. Some studies have suggested that an individual could be protected from reinfection for at least six months after natural SARS-CoV-2 infection. However, other immunological studies show a waning of antibodies (vaccine-induced or immune responses triggered after natural infection) over time.

Some studies document a decline in anti-SARS-CoV-2 CD4+ and CD8+ specific T cells within three to five months post-infection, while others report the presence of stable anti-SARS-CoV-2 CD4+ and CD8+ specific T cells for up to ten months post-infection. To date, the exact duration of immune protection after SARS-CoV-2 natural infection or by vaccination is not clear.

Strategies made by the French government to stop COVID-19 transmission

Like other countries, the French government implemented several restrictions to stop further transmission of the virus. France implemented curfews, travel restrictions, lockdowns, the obligation to work from home, among many other restrictions. They also encouraged barrier gestures that include wearing masks, keeping a distance of at least 2 meters between individuals, frequent washing of hands, avoiding gatherings of more than six people to reduce human-to-human transmission.

In France, four vaccines, namely, BNT162b2, mRNA-1273, ChAdOx1 nCoV-19 and Ad26.COV2.S received emergency use authorization (EUA), and vaccination programs commenced on January 2021. At present, more than half the population of France has completed two doses of vaccines.

Due to the rapid vaccination program that has covered the majority of the French population, the French government has relaxed public health restrictions. However, they are still encouraging the application of barrier gestures amongst individuals. A new study published on the medRxiv* preprint server focused on determining the magnitudes of a barrier gesture relaxation in France. This study estimated that all social distancing measures could be withdrawn after 90% of individuals over 65 years and 89% of the 18-64-year-olds are completely vaccinated.

As this study assumes a stable immunity post-vaccination, the predictions could be biased. In the context of the surge in COVID-19 cases owing to the transmission of the SARS-CoV-2 Delta variant, which can evade immune protection, the efficacy of the vaccines against SARS-CoV-2 variants is questionable.

A preprint version of the study is available on the medRxiv* server while the article undergoes peer review.

Impact of the relaxation of barrier gesture in France

The current study utilized an age-structured compartmental SEIR model that accounted for various factors such as vaccination, the decline in SARS-CoV-2 immunity, and the emergence of variants of concern (VoC) to predict if the relaxation of barrier gestures would result in a resurgence of severe infections. The authors of this study aimed to conduct a preliminary analysis to evaluate the impact of the COVID-19 booster dose on the older age group.

This model assumes that proneness to infection is a function of immunity status dependent on immune responses induced by previous COVID-19 infection or elicited by the COVID-19 vaccine. Researchers have obtained data containing confirmed COVID-19 cases from the French surveillance database and observed changes due to national public health policies. In this study, researchers analyzed partial and full relaxation of barrier gestures between August and December 2021 under various immunity duration assumptions.

This study has revealed the importance of maintaining barrier gestures to avoid a resurgence of severe COVID-19 infections that could far exceed health care capacities. Currently, where the rapid spread of the Delta variant has been observed and an increase in vaccine hesitancy in French people, researchers of this study emphasized the importance of promoting barrier gestures.

The current study also highlighted the importance of vaccination and stated that the available vaccines can protect individuals from severe COVID-19 disease caused by the Delta variant. Researchers stated that relaxation of complete barrier gestures can be implemented from November when, as projected, 100% vaccine coverage of the eligible French population will occur. Further, the analysis of administering vaccine booster shots to individuals over 75 does not promote relaxation barrier gesture safety, especially due to the high rate of vaccine hesitancy. Researchers of this study have stated that further modeling and more research are required to draw solid conclusions.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

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