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A healthcare worker administers the Pfizer COVID-19 vaccine to a man in Johannesburg, South Africa, on Dec. 9.SUMAYA HISHAM/Reuters

Early data show that the Pfizer vaccine is less effective against the new Omicron coronavirus variant but still provides relatively strong protection against severe illness and hospitalization from the variant, according to a major South African health insurer.

Two doses of the Pfizer-BioNTech vaccine seem to provide 33-per-cent protection against Omicron infection, compared to people with no vaccination, but the protection rises to 70 per cent in preventing hospitalization, the data suggest.

The report released on Tuesday by Discovery Health, the largest private health insurer in South Africa, is based on a review of more than 211,000 COVID-19 test results, including 78,000 test results since mid-November that were attributed to Omicron, which has been dominant in South Africa for several weeks. The study has not been peer-reviewed.

The Omicron variant is believed to be more transmissible than previous variants and more capable of causing reinfection, but early evidence suggests that it might cause milder illness.

South Africa was the first country to detect and report Omicron to the World Health Organization last month, but it is no longer the country with the largest number of cases, according to a WHO report on Tuesday. The variant has been found in at least 77 countries, in every region of the world, with community transmission already widespread in some countries.

The WHO report did not identify the country with the highest number of Omicron cases, but Britain is believed to be among those with the largest case numbers.

Britain announced that its travel ban on 11 African countries will be lifted on Wednesday. British Health Secretary Sajid Javid said it is being lifted because there is now community transmission in Britain and the Omicron variant “has spread so widely across the world.”

Canada and most other Western governments still have travel bans in place for many African countries, despite sharp criticism from scientists and health experts who say the bans are pointless. They have devastated the tourism industries of southern African countries in their most important month of the year.

Federal Transport Minister Omar Alghabra said in an interview that Ottawa is reviewing the latest data. “We will adjust our border measures as we learn more,” he said. “Stay tuned as discussions as unfolding. We could change at any moment.”

The report by Discovery Health in South Africa found that two Pfizer doses had provided 80-per-cent protection against COVID-19 infection before the emergence of Omicron. This dropped to 33 per cent for Omicron.

The drop in protection against hospital admission was much less steep. Two doses of Pfizer provided 70-per-cent protection against hospital admission from Omicron, compared to 93 per cent for earlier variants. (The WHO considers a vaccine effective if it provides more than 50-per-cent protection.)

People wait to be vaccinated by a member of the Western Cape Metro EMS at a mobile 'Vaxi Taxi', which is an ambulance converted into a mobile COVID-19 vaccination site, in Cape Town, South Africa, on Dec. 14.Nardus Engelbrecht/The Associated Press

“We are extremely encouraged by the results of Discovery Health’s analysis,” said Glenda Gray, president of the South African Medical Research Council, in a statement on Tuesday.

“It is extremely important to be able to demonstrate to the public that in a real-world setting – in the presence of a highly transmissible new COVID-19 variant – the Pfizer-BioNTech vaccine provides good protection against severe disease and hospitalization.”

The data also showed that Pfizer’s protection against hospital admission is maintained across all age groups, with only a slightly lower level of protection for older people, and its protection is also maintained for those with chronic illnesses such as diabetes and hypertension.

Looking at the broader trends, the report found that Omicron is producing a steep rise in new infections in South Africa, but it seems to be causing a lower increase in hospital admissions, possibly suggesting that Omicron is causing less severe illness.

Compared to the first wave of COVID-19 last year, South African adults seem to have a 29 per cent lower risk of hospital admission from Omicron, and they are also less likely to be admitted to intensive-care units, the report said.

But the WHO is warning that it would be a mistake to dismiss Omicron as merely a mild risk. “Surely we have learned by now that we underestimate this virus at our peril,” said WHO director-general Tedros Adhanom Ghebreyesus at a briefing in Geneva on Tuesday.

“Even if Omicron does cause less severe disease, the sheer number of cases could once again overwhelm unprepared health systems,” he said.

The new variant has triggered a dramatic rise in COVID-19 cases in South Africa, with a positivity rate that increased to 34.9 per cent on Tuesday. This means that more than one-third of those tested for the virus are found to be infected. A month ago, the positivity rate was less than 2 per cent.

The death rate and hospitalization rate, however, have not increased as rapidly as the infection rate, and the vast majority of those hospitalized have been unvaccinated.

Of those hospitalized, only a small percentage have need supplementary oxygen or intensive care – much smaller than in earlier waves of cases. And the average length of stay in hospital has been barely half of the previous average of nine days, according to South African health officials. But they cautioned that it is still too early in the Omicron wave to draw any definitive conclusions.

Among those infected in the latest surge is South African President Cyril Ramaphosa. His office announced on Sunday that he had the virus, although his symptoms are reported to be mild.

Across Africa, similar trends are being reported. Omicron has helped fuel a sharp rise in COVID-19 cases across the continent, with cases surging by 83 per cent in the past week – the fastest rate of increase this year. The number of deaths, however, has remained relatively low.

The biggest issue in Africa is still the low rate of vaccination, largely because of long delays in receiving vaccine supplies and difficulties in distributing doses. Only 8 per cent of Africans have been fully vaccinated – by far the lowest rate of any region in the world.

Only six African countries have reached their year-end target of vaccinating 40 per cent of their populations. An updated forecast by WHO shows that Africa, at its current pace, will not achieve its target of 70 per cent vaccination until August, 2024 – more than two years after the target date.

The slow vaccination rate is likely to mean that Africa will suffer tens of thousands of unnecessary deaths, according to Matshidiso Moeti, the WHO regional director for Africa.

“We are cautiously optimistic that deaths and severe illness will remain low in the current wave, but slow vaccine rollout in Africa means both will be much higher than they should be,” Dr. Moeti said.

With a report from Marieke Walsh in Ottawa

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