Model-based estimation of transmissibility and reinfection of SARS-CoV-2 P.1 variant

Abstract

Background

The SARS-CoV-2 variant of concern (VOC) P.1 (Gamma variant) emerged in the Amazonas State, Brazil, in November 2020. The epidemiological consequences of its mutations have not been widely studied, despite detection of P.1 in 36 countries, with local transmission in at least 5 countries. A range of mutations are seen in P.1, ten of them in the spike protein. It shares mutations with VOCs previously detected in the United Kingdom (B.1.1.7, Alpha variant) and South Africa (B.1.351, Beta variant).

Methods

We estimated the transmissibility and reinfection of P.1 using a model-based approach, fitting data from the national health surveillance of hospitalized individuals and frequency of the P.1 variant in Manaus from December-2020 to February-2021.

Results

Here we estimate that the new variant is about 2.6 times more transmissible (95% Confidence Interval: 2.4–2.8) than previous circulating variant(s). Manaus already had a high prevalence of individuals previously affected by the SARS-CoV-2 virus and our fitted model attributed 28% of Manaus cases in the period to reinfections by P.1, confirming the importance of reinfection by this variant. This value is in line with estimates from blood donors samples in Manaus city.

Conclusions

Our estimates rank P.1 as one of the most transmissible among the SARS-CoV-2 VOCs currently identified, and potentially as transmissible as the posteriorly detected VOC B.1.617.2 (Delta variant), posing a serious threat and requiring measures to control its global spread.

Plain language summary

SARS-CoV-2, the virus that causes COVID-19, can mutate into variants which might have different characteristics such as increased ability to spread. The P.1 variant, also known as Gamma, was first identified in Manaus, Brazil. Here, we use mathematical and statistical methods to model the spread of P.1 in Manaus and to determine the potential for people getting re-infected with P.1, comparing it to previous circulating variants in the region. We estimate that P.1 spreads 2.6 times more easily than these other variants and that nearly a third of cases over the period studied were reinfections with P.1. These findings help us to understand whether P.1 is likely to be more difficult to control than other variants and what sort of measures might be needed.

Abstract

Coutinho et al. use genomic and epidemiological data from Manaus, Brazil, to estimate the transmissibility and potential for reinfection with the SARS-CoV-2 variant-of-concern P.1 (gamma). Using mathematical modelling, the authors estimate that P.1 is 2.6 times more transmissible than previous SARS-CoV-2 variants circulating in Manaus and underlies a large proportion of reinfections in Manaus.