COVID-19 may no longer dominate the news headlines as it has over the past two years but it hasn’t gone under the radar either. Recent reports, from the UK, the US, India, China, Australia, and several European nations, indicate a steady rise in the numbers of people testing positive for COVID-19, mostly attributable to the Omicron subvariants BA.4 and BA.5- first detected in South Africa in January and February 2022, respectively. BA.5 has indeed recently become the dominant subvariant of Omicron in many countries.
The UK Health Security Agency designated BA.4 and BA.5 as “variants of concern” on 18 May 2022, based upon “an apparent growth advantage over the previously-dominant Omicron BA.2 variant”. The ZOE Covid Study app, as of 12 July 2022, has since identified 349, 773 new cases of COVID-19 in the UK, based on swab testing, while 4, 445, 058 people were predicted to have symptomatic COVID. On 12 July 2022, Lord Kamall, a Parliamentary Under-Secretary of State in the Department of Health and Social Care, informed the House of Lords that lockdown measures might have to be reintroduced in the UK if the surge was to compromise the backlog of patients waiting for treatment on the NHS. On the same day, at a media briefing, WHO Director-General Dr Tedros Ghebreyesus Adhanom referred to a “major disconnect in COVID-19 risk perception between scientific communities, political leaders and the general public”. He reminded his audience that COVID-19 remained a Public Health Emergency of International Concern and recommended that governments around the world reinstate face masks, improved ventilation, and test and treat protocols.
The worldwide increase in positive COVID-19 test results, both within the community and among those admitted to hospital, has led to variety of country-specific responses, depending on local perception of risk. By all accounts, this surge in infections appears to be associated with less virulent forms of the virus and a less severe illness of shorter duration. Upper respiratory symptoms (runny or stuffy nose, sneezing, sore throat, hoarse voice) are commoner in the presence of BA. 4 and BA.5, alongside persistent cough, headache, and fatigue. These symptoms resemble those caused by the common cold or by flu, rather than those associated with COVID pneumonia.
The high positive rate among hospitalised patients may be a reporting artefact, caused by the frequent routine testing for all people requiring hospital admission, irrespective of whether they have respiratory symptoms or not. It has thus been estimated that only around a third of those in hospital in the UK with a positive test have been admitted because of a COVID-related illness. Among those admitted to hospital directly because of COVID, rates of transfer to the intensive care unit, requirements for a ventilator, lengths of hospital stay, and death do not appear to be significantly increased, all suggesting less severe disease.
The summer surge in the UK may be linked to an increase in overseas travel, compounded by the relaxation of all national lockdown restrictions. Although there was a spike in the week following the platinum jubilee weekend, other outdoor events, music festivals, and large parties have not been conclusively linked to the resurgence of infection. The underlying reason for the surge is the altered behaviour of the new Omicron subvariants. BA. 4 and BA.5 are more transmissible, and able to evade neutralising antibodies conferred by previous infection or vaccination, because of additional spike protein mutations which allow them to infect human cells more easily. These subvariants are also less sensitive to mRNA vaccines, from waning vaccine-induced immunity as well as actual resistance to vaccines, accounting for both breakthrough infections and reinfections (infections at least 12 weeks after the first). Moderna, Pfizer, and Novavax are currently working on updated vaccines to directly target BA.4 and BA.5 and thereby improve the effectiveness of vaccination.
The strategy to deal with Omicron BA.4 and BA.5 has focused on reducing spread and protecting high-risk groups of people, with booster or even second-booster vaccination- vaccines being considered the most important tool to control the surge. People at high risk from COVID are being recommended booster vaccination and advised to wear masks in indoor public places and at crowded outdoor venues. Some scientists in the UK are also campaigning for the return of free lateral flow testing, deemed too expensive by the government, and mandatory face coverings. It seems widely accepted that not all transmission can be prevented and that extreme lockdown measures, as previously employed, are not warranted at present. As usual, responsible citizens should heed, and abide by, national public health recommendations as and when they emerge, guided by surveillance for rates of infection and the risk of serious illness among those infected.
Ashis Banerjee
PS: The UK Health Security Agency announced in a press release, on 15 July 2022, that all adults in the UK aged 50 years and over will receive COVID booster and flu vaccines during the autumn, as recommended by the Joint Committee on Vaccination and Immunisation.