Paris - The Omicron variant is causing record numbers of Covid-19 cases around the world, and though it causes less severe illness experts warn this wave still threatens to overwhelm health systems.
- Nose and throat, not lungs -
Six weeks after it was first sequenced in southern Africa, Omicron cases are smashing infection records with average new daily cases at nearly two million this week, according to an AFP tally.
At the same time, the illness caused by Omicron is proving less severe.
On Friday the French public health authority said the risk of hospitalisation was about 70 percent lower for Omicron, citing data from the US, the UK, Canada and Israel.
Experts point out that the lack of severity may be due to widespread immunity thanks to vaccination or previous infection.
But studies on animals point to another peculiarity: rather than affecting the lungs where severe Covid takes root, it seems to proliferate in the nose and throat.
This would not only explain the variant's less-dangerous symptoms but also its ability to spread quickly through coughing and sneezing.
Because of this, some experts are calling for better mask protection and Austria on Thursday made medical grade FFP2 masks mandatory outside.
Characteristics of Omicron
- Hospitals on edge -
But even though Omicron is causing less severe illness, the surging caseload overall has scientists urging caution to keep from overwhelming health systems.
"Even if the percentage of cases with severe disease is proportionally lower, when there are record cases, that still means record numbers of people in the hospital," tweeted US virologist Angela Rasmussen on Friday.
Unlike previous variant waves, however, this one seems so far to be affecting regular hospital admissions rather than ICU capacity.
This is the case in Denmark where national health service SSI reported that between December 1 and January 1 new Covid cases rose by about 70 percent across the country.
But hospitalisations only rose by 47 percent and ICU admissions by 20 percent.
- Jab immunity weaker -
Lab tests show that antibody levels in blood samples from people vaccinated with Pfizer-BioNTech and Moderna jabs drop when faced with Omicron.
The drop is even greater in those vaccinated with AstraZeneca or Sinovac, a Chinese jab authorised in about 50 countries.
A booster seems to increase antibodies, with both Pfizer and Moderna announcing positive results from recent tests.
But nobody knows how long the booster will be effective.
This does not mean vaccines are useless against Omicron: the body has a secondary immune defence called T-cell response, which fights the virus by attacking infected cells.
This secondary response is particularly important in preventing severe forms of illness.
A recent study from South Africa showed Pfizer/BioNTech remained effective at preventing severe Covid from Omicron even after just two shots.
- Last wave? -
Some experts and officials have openly expressed hope that by spreading a less-severe Covid, Omicron could be helping the planet achieve herd immunity along with jabs.
Echoing French and Israeli counterparts, top Danish epidemiologist Tyra Grove Krause tweeted her "cautious optimism about the situation when we have overcome the Omicron wave".
The World Health Organization however is urging caution.
How do vaccines help to combat Covid-19?
"The more Omicron spreads, the more it transmits and the more it replicates, the more likely it is to throw out a new variant," WHO senior emergencies officer Catherine Smallwood told AFP in an interview Tuesday.
But even if Omicron isn't the last variant, experts think immunity from previous waves might mean the worst will soon be behind us.
"New variants may challenge us," Grove Krause said, "but with vaccines hopefully SARS-CoV-2 will turn into just another airway virus we can live normally with."
By Paul Ricard, Julien Dury