The continued decline in COVID-19 cases following the intense second wave in India has led to hope that a return to normalcy might be near. Across the country, emboldened by the fact that the festival season did not lead to a steep rise in cases, restrictions have eased and public behaviour is largely returning to normal.
The low number of cases currently in India, even as cases are rising across much of Europe , appears largely attributable to two factors. First, seroprevalence studies indicate that a large proportion of the population has already been exposed to the virus providing some level of protection to subsequent infections. Second, the immunisation campaign has gained momentum . Approximately 44% of Indian adults have been fully vaccinated and 82% have received at least one dose. What is more, scientists believe that prior infection followed by one or two doses of vaccination may have a larger protective effect than two doses of the vaccination alone.
While vaccine-derived protection against symptomatic infection is expected to decay with time, current research suggests that breakthrough infections in fully vaccinated individuals are reduced in intensity and duration, compared to cases in individuals who have not been vaccinated. This holds for the Delta variant as well. Other variants have raised concerns but none of them has appeared to be significantly more worrying than the Delta variant, at least until now.
What WHO says
A new variant of the SARS-CoV-2 virus was recently identified in Botswana. Called the Omicron variant , early evidence suggests that it may be responsible for the steep rise of cases in the Gauteng province of South Africa. In this region, 90% of samples from the past few weeks have been of the Omicron variant. This variant has a large number of mutations. Some of them are cause for serious concern because they may allow the new variant to evade immunity obtained from a past infection or via a vaccine. The World Health Organization (WHO) has recently labelled this variant as a ‘variant of concern’.
While the emergence of the new variant is concerning and requires extreme vigilance, there are several questions that remain unanswered at the moment. Is the variant more transmissible? Can it evade the immune system? And is the variant associated with more severe disease outcomes?
The possibility of a new, more transmissible variant of the SARS-CoV-2 virus has, of course, been the principal worry of epidemiologists. Some other recent variants, with a more limited repertoire of mutations, have raised concerns briefly, but have not risen to the level of being named a variant of concern so far. What is concerning here is that cases of the new variant have risen so sharply as to suggest that it may far outstrip the Delta variant in its ability to infect people. There are no reliable estimates of just how much more transmissible the Omicron variant is compared to previous strains of the virus. But even crude calculations suggest it could be much larger than for those strains.
When new variants can evade immunity obtained through immunisation and prior infections, there is a greater chance for breakthrough cases and further transmission. WHO has recommended studies to understand the degree to which the immune system is evaded by the Omicron variant. This is a key question for India given the high proportion of individuals with some level of immunity, mostly from infection. If these mutations do lead to greater immune escape, vaccines and treatments like monoclonal antibodies might need to be reformulated.
Luckily, RT-PCR tests should still detect the Omicron variant.
Addressing the variant
Right now, we know very little about whether the Omicron variant might lead to more severe forms of COVID-19, both in vaccinated and unvaccinated individuals. This is clearly a priority for research. Evidence related to increased severity associated with other variants, such as the Delta variant, remains largely inconclusive.
Where did the Omicron variant come from? Viruses mutate all the time and SARS-CoV-2 is no exception. What is unusual is the very large number of mutations that the Omicron variant has accumulated. This is likely a consequence of a chronic infection in an immunocompromised patient, such as one infected with HIV. A strong immune response can ultimately eliminate the virus. However, in a weakened immune system the virus will continue to multiply and mutate, changing its form to evade immune response. Given this, prioritising the elderly and immunocompromised for a future additional dose would make sense.
While a number of nations have already closed their doors to travellers from South Africa, epidemiologists worldwide recognise that these measures can only offer temporary relief. Given that a case was found in Hong Kong in a traveller from South Africa a full four days into a mandatory quarantine, and that this patient may have infected another individual who turned positive some days later, it seems very likely that cases may have already crossed borders without being detected. Israel has also reported cases, with one of them, a 32-year-old woman, already triple vaccinated with the Pfizer vaccine before testing positive. The symptoms in this case were mild.
As long as the virus circulates, the possibility remains that new variants could emerge. The best option is to reduce case numbers. For this, vaccination is an especially powerful tool. Even a single dose of vaccine can reduce dramatically the risk of hospitalisation or a worse outcome; two doses do even better. However, the current inequity in vaccine distribution means that this means of control is out of reach of most in lower and middle-income countries. While many rich countries are now arranging for booster doses to safeguard their populations, even younger and less vulnerable individuals, this policy comes at the cost of the rest of the world, where vaccine coverage remains abysmally low. More than 60 countries have vaccinated less than 25% of their population, including South Africa. It is these regions that hold the most potential for a new, more transmissible variant. Equity in the distribution of vaccines is an urgent global public health need, quite apart from being ethically and morally the right thing to do.
The Director of the Wellcome Trust, Sir Jeremy Farrar, has in a tweet, said, “South Africa needs to be praised, offered whatever support is needed and acknowledged for the quality of speed of public health and genomic science in South Africa, sharing the data immediately, supporting the region and the world....” We concur and urge that India and other countries should learn from the South African experience, making its data available in real time for the world to study, and exhibiting the highest levels of transparency. At present, we do not know enough about the variant to truly understand the potential risk that it might pose, but — as with all such things — preparing adequately for an uncertain future is key.
Brian Wahl is an Assistant Scientist at the Johns Hopkins Bloomberg School of Public Health, U.S.; Gautam I. Menon is a Professor at Ashoka University, Sonepat and at the Institute of Mathematical Sciences, Chennai. The views expressed are personal