Covid-19 variants explained and which vaccines have biggest efficacy

From Delta to Gamma, these are the Covid-19 variants moving around the world and the vaccines that are most effective against them.

These are the Covid-19 variants moving around the world and how vaccines stack up against them in their efficacy.

BETA VARIANT

Country of origin:The Beta variant which emerged in South Africa in December 2020 is 23 to 25 per cent more transmissible than the Wuhan virus.

Global spread: Beta has been recorded in 123 countries and is better at evading the defences of some Covid-19 vaccines.

Symptoms: People with this variant are infectious for 38 per cent longer than those with the original variant.

A recent study published in The Lancet medical journal cautiously concluded the Beta variant was associated with higher hospitalisation rates and a 31 per cent increased death rate in Covid cases in South Africa.

Vaccine effectiveness: Beta variant’s spike protein might allow it to escape the immune response generated by vaccines.

The effectiveness of the AstraZeneca vaccine was found to be as low as 10 per cent against this variant and South Africa stopped plans to rollout the AstraZeneca vaccine as a result.

The Pfizer vaccine is 75 per cent effective against the Beta variant and 97.4 per cent effective against severe or fatal disease.

A study in Qatar found the Moderna vaccine was 61.3 per cent effective against Beta after the first dose and 96.4 per cent effective after the second dose.

Novavax’s clinical trials showed it was 60 per cent effective against the Beta variant.

ALPHA VARIANT

Country of origin: The Alpha variant emerged in the UK in December last year and is 29 to 50 per cent more transmissible than the Wuhan virus.

Global spread: It has been reported in 178 countries and comes with an increased risk of hospitalisation.

Symptoms:People with this variant, which is believed to cause more severe disease and death than the Wuhan virus, have a higher viral load and shed the virus for longer.

Vaccine effectiveness:A Canadian study found the overall effectiveness of the AstraZeneca vaccine against Alpha was 67 per cent compared to 72 per cent against the Wuhan strain.

It is 51 per cent effective after one dose and 66 to 85 per cent after two doses

The Pfizer vaccine is roughly 90 per cent effective against Alpha compared to 95 per cent against Wuhan.

A study in 256,000 people living in Qatar found protection from the Moderna vaccine against this variant was negligible until 14 days after the first dose, coming in at 88.1 per cent. It then rises to 100 per cent effectiveness two weeks after the second dose.

A small number of people in the study suffered infections after having the Moderna vaccination and seven people died. All deaths were in people who received just one dose of the vaccine.

Novavax has reported its vaccine to be 93 per cent effective against variants including Alpha. It is 100 per cent effective against moderate and severe cases of COVID-19.

DELTA VARIANT

Country of origin:The Delta variant that emerged in India in October 2020 — and is now ravaging Australia — is 97 per cent more infectious than the original virus and doubles the risk of hospitalisation.

Global spread:Delta is currently in at least 111 countries and the World Health Organisation said its increased transmissibility means that it is likely to become the dominant variant globally over the coming months.

Fleeting contact such as walking past an infected person is all it takes for this infection to spread.

“Where the Wuhan virus might have caused 10 cases, the Delta variant could cause 80 cases in the same time, which would quickly make it impossible to control without a lockdown,” the University of Canterbury’s Professor Michael Plank said.

A Delta Plus variant, which experts fear may be even more transmissible is also spreading in some countries.

Symptoms: Delta appears to be better at attacking lung cells. A Singapore study showed infection with Delta variant was associated with higher odds of oxygen requirement, intensive care unit (ICU) admission, or death. And the risk of pneumonia was 1.88 times higher.

Loss of smell and a cough were the key symptoms of the original version of Covid but people with the Delta variant are more likely to experience symptoms of a common cold.

A symptom-tracking app used by four million people in the UK (ZOE Covid Symptom study) records the top symptom in people under 40 as a headache, followed by a sore throat, runny nose and fever.

A cough is now only the fifth most-common symptom, and loss of smell is not listed among the top 10 symptoms.

Vaccine effectiveness:The Pfizer, AstraZeneca and Moderna vaccines do work against the Delta variant but not as effectively as they do against the original Wuhan virus.

People are 33 per cent protected against symptomatic Delta after one dose of the Pfizer and AstraZeneca vaccines.

After two doses of the AstraZeneca jab protection against symptomatic cases of Delta rises to 60 per cent, this compares to the 82 per cent protection against the original Wuhan strain.

People who have two doses of the Pfizer shot are 88 per cent protected against symptomatic cases of the Delta variant compared to the 95 per cent protection against the Wuhan version.

Moderna said blood samples from fully vaccinated people produced antibodies against multiple variants and there was only a modest reduction in antibodies against the Delta variant.

GAMMA VARIANT

Country of origin:The Gamma variant that emerged in Brazil in November 2020 is 38 per cent more transmissible but it is not believed to be more deadly.

Global spread:Gamma has been found in more than 75 countries and it appears to outsmart antibodies produced by people who have had previous Covid infections.

However, Italian researchers found it was not as strong as the Alpha variant which became increasingly common at the expense of Gamma when the two were circulating in the same communities.

Symptoms:Common symptoms include headaches, sore throat, a runny nose or a fever.

The UK symptom tracker found other symptoms included fatigue, muscle aches and fever and it may cause weight loss and lung lesions.

Vaccine effectiveness:A Canadian study found Pfizer and Moderna vaccines were 61 per cent effective against Gamma 21 days after just a single dose.

Laboratory studies show the antibodies made in response to the AstraZeneca vaccine are still active against Gamma but are slightly less effective.

Originally published as Covid-19 variants explained and which vaccines have biggest efficacy