Understanding the dynamics of COVID-19; implications for therapeutic intervention, vaccine development and movement control.

Salvamani, S; Tan, H Z; Thang, W J; Ter, H C; Wa, M Shafiq; Gunasekaran, B; Rhodes, A

The COVID-19 disease is caused by the recently identified SARS-CoV-2 virus, thought to have originated in bats (Rhinolophus affinis), the virus being highly infective within the human population and spread by respiratory droplets, contaminated surfaces and close person-to-person contact. The virus is now pandemic and widely disseminated to almost every continent and nation with globally over twenty-seven million infections and over ninety-thousand reported deaths attributed to the COVID-19 disease. SARS-CoV-2 is a single stranded RNA virus, similar in structure to that of other coronaviruses and comprising three main viral proteins; membrane (M), spike (S) and envelope (E). The clinical features of COVID-19 disease can be classified according to different degrees of severity, with some patients, particularly those of older age and with long-standing chronic illnesses, developing progressive respiratory failure and acute respiratory distress syndrome requiring mechanical ventilation. In these severe cases, the disease can frequently be fatal. In addition, many infections are asymptomatic or only cause mild symptoms. As there is no specific treatment for COVID-19 there is considerable scientific endeavor globally to raise a safe and effective vaccine against SARS-CoV-2, in addition to engineering neutralizing antibody interventions. In the absence of an effective vaccine, interim measures involving movement control and lock downs of varying stringencies have been imposed, in order to control the spread of the virus. Whilst early enforced lockdown measures have been effective in reducing the spread of infection, these measures may prove to be less effective against the current and predominant strain of SARS-CoV-2, the G614 clade. Conversely, other mutations of the virus, such as the Δ382 variant could reduce the clinical relevance of infection, and therefore may reduce the need for stringent movement control, particularly once vaccines become widely available. The front runners in the race to develop an effective vaccine focus on the SARS-Co-V-2 Spike protein. However, vaccines that produce a CD4 and CD8 response to a wider range of SARS-Co-V-2 viral proteins, may be more effective. Lastly, population based studies that determine the level of innate immunity to SARS-CoV-2 existing in the community, from prior exposure to the virus or to other coronaviruses, will have important implications for the stringencies of government imposed movement control and upon the strategic delivery of vaccination programmes.