Natural Immunity More Potent than Vaccines during US Delta Wave

 A nurse prepares a dose of the AstraZeneca vaccine against COVID-19 at a vaccination center in Mexico City. PEDRO PARDO AFP
A nurse prepares a dose of the AstraZeneca vaccine against COVID-19 at a vaccination center in Mexico City. PEDRO PARDO AFP
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Natural Immunity More Potent than Vaccines during US Delta Wave

 A nurse prepares a dose of the AstraZeneca vaccine against COVID-19 at a vaccination center in Mexico City. PEDRO PARDO AFP
A nurse prepares a dose of the AstraZeneca vaccine against COVID-19 at a vaccination center in Mexico City. PEDRO PARDO AFP

During America's last surge of the coronavirus driven by the Delta variant, people who were unvaccinated but survived Covid were better protected than those who were vaccinated and not previously infected, a new study said Wednesday.

The finding is the latest to weigh in on a debate on the relative strengths of natural versus vaccine-acquired immunity against SARS-CoV-2, but comes this time with the imprimatur of the US Centers for Disease Control and Prevention (CDC), reported AFP.

The authors of the paper warned, however, against depending on infection as a strategy, given the higher risks to unvaccinated persons who weren't previously infected of hospitalization, long term impacts, and death, compared to vaccinated people.

Indeed, by November 30, 2021, some 131,000 residents of California and New York had died from Covid-19, the two states the paper, which used statistical modeling, was based on.

"Viruses are constantly changing, including the virus that causes Covid-19," the CDC said in a statement.

"The level of protection offered by vaccination and surviving a previous infection changed during the study period. Vaccination remains the safest strategy for protecting against Covid-19," it added.

The analysis was also carried out before the emergence of the Omicron variant, for which both vaccine and infection-derived immunity appear diminished, and before boosters were made widely available.

It used case data from 1.1 million people who tested positive in New York and California between May 30 to November 30, 2021, and used that to model inferences about the wider population.

Prior to Delta becoming dominant, vaccination conferred greater immunity than infection. But the relationship shifted when the variant became predominant in late June and July.

- Selection bias? -
By the week of October 3, vaccinated people who did not have prior Covid were three to four times (in California and New York, respectively) more likely to be infected than unvaccinated people with prior Covid.

In the weeks of October 13 to November 14, vaccinated people who did not have prior Covid in California, were around three times more likely to be hospitalized than unvaccinated people with prior Covid.

Protection was highest among those who had both vaccination and prior Covid.

The study could however be impacted by an effect known as "selection bias," since it excluded people who died, who were overwhelmingly unvaccinated.

Other research, including a notable paper from Israel in August, have also found that natural immunity was more potent than vaccines during the Delta surge.

But the US CDC had previously taken the opposite position, based on pre-Delta data.

"Further studies are needed to establish duration of protection from previous infection by variant type, severity, and symptomatology, including for the Omicron variant," the paper concluded.



German Backpacker Escapes Australian Bush Ordeal by 'Sheer Luck'

German backpacker Carolina Wilga lost hope of rescue after 11 nights in the Australian bush. Handout / WESTERN AUSTRALIAN POLICE FORCE/AFP
German backpacker Carolina Wilga lost hope of rescue after 11 nights in the Australian bush. Handout / WESTERN AUSTRALIAN POLICE FORCE/AFP
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German Backpacker Escapes Australian Bush Ordeal by 'Sheer Luck'

German backpacker Carolina Wilga lost hope of rescue after 11 nights in the Australian bush. Handout / WESTERN AUSTRALIAN POLICE FORCE/AFP
German backpacker Carolina Wilga lost hope of rescue after 11 nights in the Australian bush. Handout / WESTERN AUSTRALIAN POLICE FORCE/AFP

German backpacker Carolina Wilga lost hope of rescue after 11 nights in the Australian bush, and only made it out by "sheer luck", police said Saturday.

The 26-year-old walked "confused and disoriented" 24 kilometers (15 miles) away from her van after it got stuck in remote bushland in Western Australia, AFP reported.

As police searched for her by air, the backpacker's ordeal ended Friday when she managed to flag down a woman driving by who took her to police.

"She is still in disbelief that she was able to survive. In her mind, she had convinced herself that she was not going to be located," said Jessica Securo, acting inspector for the Western Australia police.

The rescue was down to "sheer luck".

"I actually spoke to Carolina this morning, so she confirmed that she was very confused and disorientated," Securo told a news conference.

"She basically looked at the direction of the sun and tried to head west, thinking that that would be her best bet of coming across someone or a road."

Wilga had been last seen on June 29 arriving in the van at a general store in the small agricultural community of Beacon, northeast of Perth.

Police found the van on Thursday, abandoned after getting stuck in dense bushland north of Beacon, with plastic orange traction tracks placed beneath the rear wheels.

"It appears that she has somewhat lost control of the vehicle, and then it's become mechanically unsound, and bogged," Securo said.

- 'Overwhelmed' -

She stayed with the van for one day before leaving the vehicle through "panic", hoping to find help.

Wilga was found "exhausted, dehydrated and hungry", suffering from cuts and bruises, but "overwhelmed" to have found someone to help her.

"She had minimal food and minimal water. From speaking to her, she has said she could have planned better."

The terrain "can be quite dangerous", Securo added.

Wilga remained in a Perth hospital and was not expected to be released on Saturday, still needing "emotional support" and treatment for some injuries.

"She's had a good night's sleep. She's had a shower. We've got her some food, which was a massive relief for her. So she's just taking it one day at a time at the moment."

The backpacker is now in "frequent communication" with her family who are relieved and thankful the Western Australian community came together to "throw every resource at locating their daughter", Securo said.

The family had no plans at this stage to travel to Australia.

Police say Wilga had spent two years backpacking around the country, and was working at mine sites in Western Australia while staying mostly at hostels.

"Carolina has told me that she loves Australia. She still has so much travel to do here. She hasn't made it over to the east coast yet, so that's still on her bucket list."