On 21 March 2021, COVID-19 continued to increase for the fourth consecutive week worldwide, with 3.3 million new cases in the week of 15 March. At the same time, the number of deaths, after declining in recent weeks, had reached a plateau of 60,000 cases. Europe and the Americas reported about 80% of new cases and deaths. After a year of pandemic, there have been 123 million cases and 2.8 million deaths (WHO, 21.03.2021). In Portugal, by 24 March, the cumulative number of COVID-19 cases was around 820 thousand and the death toll was around 17 thousand (DGS, 24.03.2021).
The World Health Organization considers the situation to be very worrying. The vaccination campaigns and the emergence of variants are likely to have an impact on the evolution of transmission patterns.
Vaccines are the best way to stop the pandemic and, currently, three vaccines are available for COVID-19. The priority is to save as many lives as possible and to reduce hospitalizations, which have created enormous pressure on our National Health Service. For now it is necessary to give priority to the most vulnerable people, the elderly, who represent about 87% of deaths by COVID-19. A successful vaccination programme will protect people from serious illness and allow them to return to a life close to normal. For that to happen, it is necessary to move forward early and without delay. However, until these objectives are achieved, it is necessary that each person does his or her part - stay, whenever possible, at home, wash hands, wear face masks, keep social distance and limit social contact. Testing, screening and isolating, including those infected but asymptomatic, is crucial to keeping the virus under control.
The emergence and prevalence, in some regions, of multiple new, highly infectious variants, has had a dramatic global impact on the epidemiology of SARS-CoV-2. In addition to increasing transmissibility, these variants are more virulent and have the potential to evade immune memory induced by vaccines or by the infection itself. It is believed that these variants may originate in individuals with reduced immune capacity to control the virus, but the factors leading to their spread and the ability to replace other circulating variants are poorly characterized.
The most important variants are B.1.1.7, B.1.351 and B.1.1.28.1, which were, for the first time, identified in the United Kingdom, South Africa and Brazil, respectively. These variants, with greater transmissibility capacity than the circulating older variants, have increased risk of hospitalization, greater severity and mortality (except for variant B.1.1.28.1.) They also reduce neutralizing capacity using the plasma of convalescents from COVID-19, and patients have a potential risk of reinfection (except for B.1.1.7).
As for the potential impact on vaccine efficacy, no significant changes have been identified in the neutralizing capacity induced by Moderna, Pfizer-BioNTech and Oxford-AstraZeneca vaccines in relation to variants B.1.1.7 and B.1.1.28.1. The Moderna, Pfizer and Oxford-AstraZeneca vaccines showed a substantial reduction in neutralizing activity regarding variant B.1.351. As for disease prevention, no changes in efficacy in relation to the vaccines from Oxford-AstraZeneca and Pfizer, regarding variant B.1.1.7 have been identified. As regards variant B.1.351, the AstraZeneca vaccine appears to have some reduction in efficacy for COVID-19 disease, and it is plausible that the effect for severe disease is also partly compromised.
Studies on the impact of these vaccines in preventing infection are limited, but the effectiveness against these variants appears to be reduced.
All viruses, including SARS-CoV-2, have a tendency to evolve, resulting in the emergence of new variants, most of which have no direct benefit to the virus or impact on public health. The potential for virus mutation increases with rising frequency of infections in humans and animals. Reducing the transmission of SARS-CoV-2 through disease control, as well as preventing its introduction into animal populations, are the most important aspects for reducing the emergence of mutations, which can have negative public health implications. On the other hand, in addition to vaccination, strengthening physical distance and other public and social health measures are of the utmost importance for reducing the spread of SARS-CoV-2, including the new variants.
Prof. Francisco Antunes
Infectologist/FMUL Retired Professor
