The Covid-19 vaccines have undoubtedly saved hundreds of thousands of lives across the globe since the inoculation drive was launched in the USA on December 14, 2020, about one year after the outbreak of novel coronavirus pandemic. Whereas it took decades for scientists to devise newer vaccines in the past, it was amazing that they could develop safe and effective Covid-19 vaccines in a single year. However, their limitations are also becoming apparent now in the wake of newer variants of the virus like Alpha, Beta, Delta and Omicron, popping up at different corners in various continents. As the Omicron variant rings alarm-bells across the globe, scientists in various locations are now working hard to develop a universal vaccine that can combat newer varieties of the coronavirus in the future. The aim is to fight effectively not only SARS-CoV-2 or novel coronavirus, but also other potential pandemic-causing viruses.
It was during the mid-1960s that the human coronaviruses were first identified, but they rarely caused severe diseases in the past. That changed dramatically in 2002, when a new coronavirus SARS-CoV linked to cave-dwelling bats appeared in China and then spread to 29 countries by causing a fatal respiratory illness. This SARS (Severe Acute Respiratory Syndrome) epidemic infected about 8 thousand people and resulted in over 770 fatalities. Another new coronavirus MERS-CoV emerged in Saudi Arabia ten years later, again originating from bats. This MERS (Middle East Respiratory Syndrome) virus infected over 2 thousand people in 37 countries and killed about 900. And finally, the danger posed by coronaviruses originating from animals has now become more obvious with the outbreak of SARS-CoV-2.
The novel coronavirus that causes Covid-19 has mutated multiple times since the pandemic's commencement, giving rise to different variants. As most vaccines were designed to recognise the spike protein or parts of it in the original virus, the more mutated variants like Omicron are more proficient at evading protections offered by vaccines. Consequently, although current jabs are expected to provide safeguards against severe illnesses owing to infections from existing variants, scientists still do not know how effective these would be against newer variants that might emerge in the future. Therefore, researchers are trying hard to develop vaccines that may have universal application and can simultaneously combat all known and unknown variants of the virus.
The National Institute of Allergy and Infectious Diseases (NIAID) under the National Institutes of Health (NIH) of the USA have already allocated USD 36 million to three institutions for the above-mentioned purpose under a pan-coronavirus vaccine development programme. These entities are: the University of Wisconsin at Madison, Brigham and Women's Hospital at Massachusetts, and the Duke University of North Carolina. Besides, the Walter Reed Army Institute of Research (WRAIR) of the US Army is also striving to develop a pan-coronavirus nanoparticle vaccine by attaching virus-spikes to a protein called ferritin. It has been named 'Spike Ferritin Nanoparticle' (SpFN) vaccine.
One should not, however, ignore the fact that the currently available Covid-19 vaccines are amazing scientific feats achieved within a single year. After targeting a new virus, multiple highly effective vaccines have been developed reaching billions of people across the globe. New approaches like messenger RNA (Pfizer-BioNTech and Moderna) and adenovirus vectors (Janssen) were applied for the first time in history, thereby making a huge leap in vaccine technology. Scientists are now calling for an even bigger leap in technology by envisioning a universal coronavirus vaccine. This is mainly because, the protection from existing Covid-19 vaccines fades over time as the virus changes or mutates in ways that makes it harder for the immune system to neutralise it.
Prior to the Covid-19 pandemic, a standard formula was followed in developing vaccines, which was to expose the immune system to virus threats by injecting weakened or dead viruses, or virus segments, into the body. But now, the mRNA and adenovirus vaccines pass on genetic instructions to human cells, thereby enabling them to produce fragments of the novel coronavirus that cause the disease. These components are used for target practice by the immune system and the system has an action-plan when the real pathogen arrives subsequently. But the challenge here is that, the prior target practice does not always translate into decisive action from one variant to another because of their specific nature. Therefore, when a virus mutates, the vaccines may become less effective in curbing the disease. The need arises therefore for a vaccine that can address a spectrum of potential threats.
Scientists are adopting two broad strategies for achieving this objective. The first one is to train the body to recognise a mosaic of spike proteins from numerous variants. This strategy attempts to combine multiple antigens (substances evoking immune response) in a single shot. It involves taking as many spike proteins from as many differing coronaviruses as possible and then accommodating them all in a virus-like nanoparticle. After getting exposed to these samples, the immune system is likely to fill up the blanks and cover most, if not all, potential variants of the virus. The WRAIR of the US Army is pursuing this strategy by attaching various SARS-CoV-2 spikes to the protein called ferritin. The vaccine is currently in its early clinical trial phase.
The second plausible strategy for developing a universal vaccine is to vaccinate against parts of the coronavirus that do not mutate. This approach targets other parts of the virus that remains the same even when the virus mutates, which are called the conserved parts. When these parts are targeted, it is likely to result in protective efficacy against any of the potential viruses, as antibodies can act against them. These antibodies are described as non-neutralising ones, as although they do not prevent infection, they recruit other actors in the immune system like B and T cells that eliminate the infected ones. As a result, a dangerous coronavirus can be turned into a mere bug that can cause only minor illness.
However, historical records show that science has never been able to produce a universal vaccine for any kind of disease. Besides, while vaccines are critical means for keeping infectious diseases at bay, even an effective universal vaccine may not be sufficient to eradicate a pandemic or prevent the next one. Moreover, there is no guarantee about how long the protection from such a vaccine would last. Even if a universal vaccine succeeds in covering all coronaviruses, the immunity it elicits may wane subsequently. But durable immunity is also critical alongside widest coverage of the vaccine.
We should also keep in mind that coronaviruses are not the only group of viruses that pose a pandemic threat to mankind. Influenza has also been high on the list of potential threats. In fact, the previous four pandemics were caused by influenza viruses, viz. 'Spanish Flu' in 1918-19, 'Asian Flu' in 1957-58, 'Hong Kong Flu' during 1968-69, and 'Swine Flu' in 2009-10. The World Health Organisation (WHO) has therefore warned: "The world will face another influenza pandemic - the only thing we don't know is when it will hit and how severe it will be". The scientists Matthew J. Memoli and Luca T. Giurgea of the Infectious Diseases Laboratory at US National Institutes of Health are now conducting Phase-1 trial for a universal flu vaccine, which has so far proved very effective against all flu viruses in animals. This vaccine may ultimately replace the seasonal flu shots by requiring additional one or two boosters in a lifetime. Other researchers are also hard at work on developing an arsenal of vaccines that can offer protection against 20 virus families including those causing Zika, Nipah, and Chikungunya.
The reality is that our animal kingdom on earth is teeming with pathogens including viruses, and as many as 1.7 million undiscovered viruses live in mammals and birds. Of these, up to an estimated 827 thousand can infect humans, an UN-backed consortium of researchers has claimed. And as mankind continues to encroach upon animal habitats through deforestation, urban expansion and animal trafficking, the risk of another pandemic only grows gradually. As an infectious disease researcher - Kayvon Modjarrad of the Walter Reed Army Institute of Research - puts it, "The viruses have been around for billions of years, we've been around for 200 thousand, maybe. If this is a foot race, and we start at the same starting line as the viruses, we're always going to lose".
Dr Helal Uddin Ahmed is a retired Additional Secretary and former Editor of Bangladesh Quarterly.
hahmed1960@gmail.com