Seychelles’s Covid Mysteries Pit
Anti-Vaxxers Against Scientists
Cases in the world’s
most vaccinated nation are ticking up, forcing researchers to wage war against
misinformation on whether jabs are effective.
May 27, 2021, 12:01 AM EDT
A sign for social distancing in Seychelles on Jan. 12.
For epidemiologists, the past year and a half has been a
voyage of discovery. Recently their journey aboard SARS-CoV-2 took an
unexpected turn toward Seychelles, a palm-fringed archipelago in the Indian
Ocean with fewer than 100,000 inhabitants. A country that few could pinpoint on
a map suddenly became internet-famous as the most vaccinated nation on Earth,
with 64% of the population having received the requisite two shots. Yet
to the surprise of virologists—and the dismay of the government, which had been
counting on the immunization drive to reopen the tourism-dependent economy—the
infection count has been ticking up. As of May 13 a third of active cases—about 900 in all—were among residents who’d been fully vaccinated.
Vaccine skeptics pronounced themselves vindicated, while
international health experts have been scrambling to answer a host of questions
without the benefit of robust data. Did one or both of the vaccines used in
Seychelles fail? Has herd immunity not been reached? Is the nation grappling
with a more infectious variant capable of evading the defenses that certain
types of vaccines provide?
“So what’s going on?” asked Raina MacIntyre, professor of
global biosecurity at the Sydney campus of the University of New South Wales,
during an online presentation on May 18. “It’s probably that the herd immunity
threshold hasn’t been reached, plus or minus, if it’s the South African variant
in there.”
The answers to the questions MacIntyre and other experts are
posing may influence the future course of the pandemic. For starters, the tiny
nation has become a test case for
two of the world’s most widely used vaccines. In the Seychelles, 57% of
the vaccinated population received
Sinopharm’s shot, and 43% got the Covishield vaccine developed by AstraZeneca Plc. Sinopharm’s inoculation has been
donated or sold to countries around the globe, including Indonesia, Venezuela,
and Zimbabwe; Covishield makes up the bulk of shots distributed to poor nations
in Africa and elsewhere through the Covax initiative, which seeks to make
vaccine distribution more equitable.
What’s happening in Seychelles is very different from the experience of Israel, the second-most
vaccinated nation, where Covid-19 infections have plummeted. The contrast could
yield crucial insights into the efficacy of the different types of
immunizations. In Israel the dominant vaccine was the messenger ribonucleic
acid shot made by Pfizer Inc. and BioNTech SE.
The pandemic has seen mRNA
vaccines— Moderna Inc. makes another—being used in scale for the first
time. Data from clinical trials so far suggest they are better at stopping
Covid, tackling variants, and preventing the virus from spreading in the
community. Sinopharm’s and AstraZeneca’s vaccines rely on more traditional
methods, and their shots have been shown to have lower efficacy in studies.
What’s also apparent, so far, is that though there’s been a surge
in cases in Seychelles, very
few people are getting seriously ill. “We have only a few people needing
intensive care. Two out of 40” in hospitals, said Seychelles President Wavel
Ramkalawan in a May 10 interview. “The vaccine will protect people from getting
serious symptoms.”
Still, more answers are needed. The government hasn’t
disclosed what vaccine was administered in the breakthrough cases that make up
a third of the total count. No agency has done any genomic sequencing to
determine which variant is dominant on the islands, though the one first
identified in South Africa, B.1.351, was detected in Seychelles in February.
On May 13, Jude Gedeon, the country’s public-health
commissioner, said samples were to be sent to the Kenya Medical Research
Institute for testing. The World Health Organization is also taking action. “We
are very concerned, and we are sending a multidisciplinary team there to help
the Seychelles government address the situation,” says Richard Mihigo, program
area manager for immunization and vaccine development at the WHO’s regional
office for Africa in Brazzaville, Republic of Congo. “We are also in discussion
with the government to conduct a vaccine effectiveness study.”
The situation in Seychelles also offers a fresh reminder
that our understanding of herd immunity—the
theoretical threshold at which the virus can’t find enough hosts to keep
spreading—continues to evolve. Scientists once estimated that 55% to 82% of the
population would need to have immunity against SARS-CoV-2, either from
recovering from an infection or through vaccination. But 17 months into the
pandemic, there’s recognition that the threshold may vary depending on the
susceptibility of a population to the circulating strains, adherence to
physical distancing, mask-wearing, and other practices known to reduce
transmission, as well as the season—epidemics typically worsen as either
colder or hotter weather encourages people to congregate indoors.
“It’s probably not likely that we are going to drive to zero
the transmission of this virus or have it disappear,” says Jennifer Nuzzo, an
epidemiologist and senior scholar at the Johns Hopkins Center for Health
Security in Baltimore. Still, she sees vaccines “doing the thing that we care
most about, which is preventing serious
illness.”
Lessons from Seychelles could be valuable to other countries
in assembling their own vaccine arsenals, through purchases or donations—or a
combination of the two, as the tropical nation did. “It’s about quality
vaccines that are shown to be effective against your variant,” says Glenda
Gray, president of the South African Medical Research Council and co-lead of a
Johnson & Johnson Covid vaccine trial in the country.
Finance Minister Naadir Hassan, who had to steer
Seychelles’s economy through a 13% contraction in 2020, says the government
cannot afford to stand still while it awaits answers to these Covid riddles.
The country is “an open, vulnerable economy,” he said in a May 13 interview.
“The country needs to be safe, and the country needs to be open.”
No comments:
Post a Comment