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Omicron vs Delta COVID Variants: What Early Data Says

Can comparing its early trajectory to that of Delta's help decode Omicron, the new COVID variant of concern?

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Coronavirus
4 min read
Omicron vs Delta COVID Variants: What Early Data Says
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Only two weeks old and Omicron, the new COVID variant, has already taken over the news. Apart from being extensively discussed, the latest variant of concern to emerge after the devastating Delta variant has also sparked concerns of a pandemic do-over.

While India braces for a possible third wave, other countries like France and Germany are already seeing early signs of a fourth and fifth wave.

We don't know much about the variant, but what we do know is that it spreads. Fast.

As of 9 December, Omicron has spread to more than 63 countries according to the World Health Organisation (WHO).

The above map shows the percentage of Omicron variant cases identified out of the total samples used for gene sequencing in the countries on 13 December 2021.

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While data is unavailable for many countries, in the ones where Omicron has been detected, the spread has been rapid.

In South Africa, in particular, where scientists first sequenced and identified the variant, Omicron has now overtaken Delta as the dominant variant, with 100 percent of the samples that were sequenced turning out to be that of Omicron.

This doesn't mean that all the COVID cases in South Africa are of the omicron variant or that Delta is no longer the overall dominant variant. It just means that of all the samples that went through gene sequencing on 13 December, a 100 percent of them were found to be Omicron.

Delta vs Omicron

Omicron is still in the early stages, and like experts have reiterated, time and further research will be needed to discern the actual extent of its impact.

But a comparison of its early trajectory with that of Delta —now well documented, may give us some clues as to how this new variant of concern may behave in the future.

Infectiousness:

The Delta variant—the variant behind India's devastating second wave—quickly dominated the world COVID charts thanks to how rapidly it spread, beating out the other VOCs at the time, Alpha and Beta.

However, looking at the early trajectory of Omicron's spread points to it being far more infectious than Delta.

The above graph shows the shift in South Africa's COVID landscape, where in a matter of a couple of weeks, Omicron has considerably driven up the daily caseload of the country.

The country saw a steep rise in cases of Delta in June 2021 with the VOC making up close to 80 percent of the analysed samples by the end of the month and over 96 percent in the beginning of November.

The rise in cases of Omicron, however, has been much sharper in a shorter duration of time.

In other countries where the variant has been detected, its share out of the analysed sequences remains in the single digits, but experts advise erring on the side of caution based on the situation in South Africa.

Breakthroughs and Re-infections:

Increasing research has found that the variant is capable of circumventing vaccine protection and even causing reinfections in people with natural immunity.

This was an issue with the highly contagious Delta variant as well.

Although India's overall seroprevelance was not particularly high at the time, a huge number of fully vaccinated people were also infected with COVID during the second wave which was dominated by the Delta variant.

A preprint study conducted by Indian researchers in collaboration with the Cambridge Institute of Therapeutic Immunology & Infectious Disease found that the Delta variant showed an 8-fold reduction in sensitivity to antibodies, increasing the risk of breakthrough infections.

Other studies conducted in the UK, Israel, and other places have also alluded to this.

However, researchers of the first real world study on breakthrough COVID cases from Omicron pointed out that studies from South Africa and Germany, as well as several unpublished data from the UK, have found a 10-fold reduction in neutralising activity (against Omicron) in those who have received 2 doses of the Pfizer vaccine compared to the Delta variant.

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Hospitalisation & Deaths:

In spite of the swifty rising number of cases, reinfections and breakthrough infections, cases of Omicron so far have largely been asymptomatic or causing mild symptoms.

However, past data from the second wave and experts suggest this shouldn't be a reason to let our guards down just yet.

Although the rate of increase of deaths being recorded per day was gradual in the case of Delta, two months into the second wave, India went on to record upwards of four thousand deaths per day.

Which means a low number of deaths at the beginning doesn't necessarily predict the future course of a variant, as there tends to be a lag between cases starting to go up and the emergence of serious illnesses and deaths.

The bottom line

Of course, in the case of Delta, there were many other factors like low vaccination rate (still an issue in many parts of the world) and low seroprevalence that were major contributing factors that led to the high number of severe cases, hospitalisations and fatalities.

In a live interaction with FIT, Dr K Srinath Reddy, president, Public Health Foundation of India, formerly head of the Department of Cardiology at AIIMS, explained,

"In India we have had a substantial exposure to the delta variant in the second wave, and therefore, the immunity created against the delta variant would carry over, to some extent to this variant as well."
Dr K Srinath Reddy, president, Public Health Foundation of India, formerly head of the Department of Cardiology at AIIMS

Speaking to FIT for another article, he said, "If this is corroborated in larger studies, it might indicate that the virus is evolving towards a more infectious but less virulent form."

But he also warned that these are merely hypothesis at this point, and further studies will be needed to make assertions.

In the same article, virologist, Dr Shahid Jameel explained, "the early signs are at least encouraging that the virus may not be causing severe disease. But, let us not be complacent, let us be concerned, but not get paranoid."

"No variant can penetrate your masks," said virologist, Dr Shahid Jameel speaking to FIT for a previous story.

So the best way to protect yourself from Omicron is to keep your masks up, maintain hand hygiene and get vaccinated if you haven't got both your primary doses yet.

(Subscribe to FIT on Telegram)

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