And breakthrough Omicron infections boost protection to previous variants.
Welcome to The Medical Republic’s Covid Catch-Up.
It’s the latest covid-19 news in one convenient post. Email bianca@biancanogrady.com with tips, comments or suggestions.
4 April
- Easing quarantine with cases increasing risks health system overload, health chiefs warn.
- Breakthrough infection with Omicron boosts neutralising activity against all variants.
- Double-dose of Pfizer offers nearly 80% protection against critical Omicron infection in adolescents.
- Updated flowchart on covid drug treatments for at-risk adults.
Easing quarantine rules for close contacts when covid cases are still on the rise will cause significant disruptions to the health system and societal functioning, the Australian Health Protection Principal Committee has warned.
The advisory body, which consists of all state and territory Chief Health Officers and Australian Chief Medical Officer, said in a statement that infection rates have increased in recent weeks, both as a result of the more infectious BA.2 Omicron subvariant and waning immunity, but also as states have relaxed quarantine rules for close contacts and the rollout of booster vaccinations has slowed.
Given this, they advised that now is not the time for further easing of transmission reduction strategies, and Australia should continue with measures such as testing of all symptomatic people with RAT or PCR and seven days isolation for close contacts, at least until the peak of this wave has passed.
“Making changes, including changes to quarantine settings, that will result in increased transmission in the community at a time when cases are already increasing or are at their peak, may result in further disruption to the health system,” they wrote.
AHPPC also recommended that anyone with acute respiratory symptoms should stay home, regardless of whether they test negative, and advised against any delays in influenza vaccinations for the broader community.
Breakthrough infections with Omicron broaden the neutralising antibody response to also boost antibody and immune protection against previous variants, research suggests.
A non-peer-reviewed preprint study, published on BioRxiv, compared the neutralising antibody profiles in serum taken from people who were double- or triple-vaccinated with the Pfizer vaccine and had not experienced covid, those who were double- or triple-vaccinated with Pfizer and had experienced a breakthrough Omicron infection after either their second or third dose.
The researchers found that serum taken from those who were double- or triple-vaccinated and had experienced breakthrough infections was effective at neutralising both Omicron BA.1 and BA.2, as well as previous variants of concern including Alpha, Beta and Delta strains.
In comparison, serum from individuals who were double-vaccinated but Omicron-naïve had reduced neutralising activity against Beta and Delta, and almost no neutralising activity against either Omicron subvariant. Those who were triple-vaccinated but never infected with Omicron had higher neutralisation activity against Alpha, Beta and Delta, but the neutralising activity was relatively lower against Omicron BA.1 and BA.2.
“Our findings show that Omicron breakthrough infection of vaccinated individuals boosts not only neutralising activity and [B memory] cells against Omicron but broadly augments immunity against various VOCs,” the authors wrote.
A double dose of the Pfizer vaccine is 68% effective at preventing hospitalisation from Omicron infection in children aged 5-11 years and nearly 80% effective against critical disease in adolescents, a study has found.
Writing in the New England Journal of Medicine, researchers report the findings of a study of 1185 children and adolescents hospitalised with covid – Delta or Omicron – and 1627 controls hospitalised for other reasons.
Among adolescents, two-doses of Pfizer vaccine were 92% protective against covid-associated hospitalisation with Delta, but only 40% protective against hospitalisation with Omicron. It also offered 96% protection against critical infection with Delta and 79% protection against critical infection with Omicron.
Among children aged 5-11, two doses of the Pfizer vaccine were 68% effective at preventing hospitalisation with Omicron.
“Our study provides strong evidence for the benefits of vaccination in preventing the most severe forms of disease related to the Delta and Omicron variants in children and adolescents,” the authors wrote.
The living guidelines on drug treatments for adults with mild to moderate covid but who are at risk of severe disease have been updated.
The National Covid-19 Clinical Evidence Taskforce has released a new version of its decision-making flowchart for adults not on oxygen, which includes detailed information on each of the drug treatments currently available, when and how to use them, and possible contraindications.
