Of variants, vaccines and inequity

Vaccine inequity that leaves large populations unvaccinated raises the risk of dangerous variants emerging which will affect the whole world. — Reuters

Once upon a time there was a coronavirus. It was a nasty little thing that kicked off an epidemic in East Asia and made lots of people really sick. Eventually, human immune systems built enough defences against it. And then it became no more of a threat than the common cold.

No, I’m not talking about Covid-19 but about an ancient coronavirus that caused an epidemic 20,000 years ago. Scientists pieced together this story by analysing human genomes. So severe was the epidemic that it left its mark on human DNA.

Could this be the happily-ever-after scenario that unfolds in the future for Covid-19? Will the new Omicron variant hasten or ruin the ending? It’s hard to say. Other coronaviruses may shed some light.

As the ancient epidemic shows, coronavirus epidemics have occurred before. Of the hundreds of existing coronaviruses that circulate among animals, seven infect humans: four cause mild colds, while three that adapted to humans (from animals) in the last two decades – Covid-19, SARS (severe acute respiratory syndrome) and MERS (Middle East respiratory syndrome) – cause severe respiratory disease.

Viruses jumping from animals to humans spell bad news because they’re often more virulent as they’re new to humans. In fact, most deadly new infectious diseases are zoonotic (of wild animal origin), including AIDS (from monkeys), Ebola (bats) and avian flu (wild birds). In the late 1990s, the Nipah virus went from flying foxes to pigs to humans in Negri Sembilan. Viruses crossing species are now a growing threat due to deforestation, destruction of natural habitats, and the trade in and consumption of wild animals.

As for the four older coronaviruses, we’ve all had them from young as common colds (although rhinoviruses cause most colds). Studies in China found 70% of adults had antibodies for these four coronaviruses. However, these viruses mutate quickly, becoming less recognisable to us, while levels of antibodies to neutralise them may fall. Thus we can get reinfected – but not badly, because some immunity to fight them remains (in memory B and T cells).

So while immunity to reinfection may wane, our immunity to severe forms of the diseases lasts longer. Likewise, after Covid-19 vaccines or infections, some reinfections may occur, but severe illness is less likely.

Some virologists believe SARS-CoV-2, the virus which causes Covid-19, could eventually evolve to cause only a mild cold. This could take years or decades, although vaccination is speeding things up.

But nothing is certain. SARS-CoV-2 could mutate to become more lethal or to evade our immune system. There’s no guarantee of a milder virus. Look at HIV – it still kills, 40 years after it made its first appearance.

The appearance and spread of the Omicron variant of Covid-19 in dozens of countries is now causing much alarm. With over 50 mutations, many around the spike protein which vaccines target, the fear is that it will lower vaccine efficacy, being so altered. But mutations don’t always work in synergy; some may cancel each other out. Only real-world data over time will tell us what this means.

Meanwhile, more countries need to track variants. We should thank South Africa for its excellent surveillance, rather than slap on ill-thought travel bans that come too late.

The Omicron strain could cause more reinfections. But experts believe the vaccines will still protect us against a severe form of the disease, pointing to the experience with other variants.

Even if vaccine efficacy does drop significantly, we will still not go back to 2020, when humans were immunologically “naïve” to SARS-CoV-2. Remember, we’ve since had eight billion vaccine doses and millions of Covid-19 infections. That gives us some measure of immune protection.

Interestingly, one study found the Omicron variant carries a genetic sequence common in the coronaviruses that cause colds. This could mean it transmits more easily but causes only a mild form of the disease.

Early data does indicate the Omicron variant causes mostly mild cases. One district hospital in Pretoria in South Africa reported most Covid-19 patients didn’t require oxygen and, in fact, were mostly admitted for other reasons.

But it’s too early to tell. We still need much more data and across many different populations, especially older and vaccinated ones, unlike South Africa’s young and mostly unvaccinated population.

In the meantime, the best we can do to protect against the Omicron variant is to ramp up our immunity through vaccination. Vaccine inequity is shocking – only 6% of Africa is vaccinated. Having the virus spread across such unvaccinated populations raises the risk of dangerous variants emerging which will affect the whole world.

There are also the anti-vaxxers, driven by false scare stories on social media. What I find strange is some of them support untested treatments and take strong medicines. They worry about the long-term effects of mRNA vaccines, but mRNA is cleared from the body days after vaccination. They’re banking on “natural” immunity, but that’s not always enough. Some people have a gene (LZTFL1) or chromosome 3 variant that, respectively, doubles the risk of death or severe disease.

We know vaccines help reduce severe disease and death. We don’t know how this pandemic will play out. But if vaccine inequity and hesitation continue, you can bet the ride to the end will be much rougher.

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Human Writes columnist Mangai Balasegaram writes mostly on health but also delves into anything on being human. She has worked with international public health bodies and has a Masters in public health. Write to her at [e-mail]. The views expressed here are entirely the writer's own.