Omicron variant papers

Omicron variant doesn’t escape T cell responses

A Nature news article summarises the results of studies showing the effectiveness of T cells against Omicron.

Vaccine-related papers

Good protection against serious Covid from 3rd vaccine dose in over 65s, at least for 10 weeks

A third vaccine dose provides high levels of protection against hospitalisation for those over 65, although effectiveness against symptomatic infection waned quickly. Ten weeks after third doses, effectiveness against symptomatic infection was about 30% for a Pfizer/BioNTech “booster”, but higher if the third dose was the Moderna vaccine.

Effectiveness against hospitalisation was about 98% at 10 weeks. This short paper, from the UK, notes that the sample sizes were small, although it does not state them. The paper has not yet been peer reviewed.

Little decline in effectiveness against severe Covid over 20 weeks after two vaccine doses

Both the Pfizer/BioNTech and AstraZeneca/Oxford vaccines showed little waning in effectiveness against preventing severe Covid-19 over 20 weeks. Effectiveness against hospitalisation after two doses was 80% for the AstraZeneca vaccine and 92% for the Pfizer. Waning was greater for those over 65 and those with other health conditions.

Ten weeks after the second dose protection against symptomatic infection for both vaccines declined, and at 20 weeks was 44% for AstraZeneca and 66% for those who received the Pfizer vaccine. This UK study included several million people who were tested for infections. The paper was published in the New England Journal of Medicine.

Vaccines reduce levels of infectious virus

While viral RNA levels of the Delta variant can be similar between infected vaccinated and unvaccinated people, a study found that the level of infectious virus is lower in those who have been vaccinated. Vaccinated people also cleared the virus more quickly, so were likely to be less infectious.

The Delta variant showed higher levels of infectious virus than seen for an early viral variant. Infectious viral loads of the Omicron variant in vaccinated people were similar to Delta, so the authors conclude that the higher transmissibility of Omicron is not due to higher viral loads. The paper has not yet been peer reviewed.

Vaccines safe and very effective for pregnant women

A Scottish study reports that vaccines are highly effective in preventing infections and severe Covid-19 in pregnant women. Health records were used to compare infections and outcomes of vaccinated and unvaccinated women. Seventy seven percent of pregnant women who became infected were unvaccinated, and 91% of hospitalisations and 98% of severe cases were unvaccinated. Baby deaths before or shortly after birth were all from unvaccinated mothers. Vaccines involved in the study were Pfizer, Moderna and AstraZeneca. The paper was published in Nature Medicine.

Few serious adverse reactions to Pfizer vaccine in children under 12

Serious adverse effects from the Pfizer/BioNTech vaccine are rare in children under 12, according to US CDC data. Only 2% of vaccinated 5-11 year olds reported serious adverse reactions to the Vaccine Adverse Event Reporting system, compared with 8% for 12-18 year olds.

Fever was the most common serious adverse reaction in under 12s, and reports of myocarditis were very low. The results, presented as a set of slides, have not yet been peer reviewed.

Non-vaccine-related papers

Short life for virus in aerosols

The infectivity of SARS-CoV-2 in aerosols can decline rapidly. In laboratory experiments the majority of viral particles were inactivated within 10 minutes. Infectivity loss was greatest at low levels of relative humidity. The paper has not yet been peer reviewed.

Caution required when interpreting rapid test results

Testing of rapid diagnostics tests for SARS-CoV-2 infection concludes that the likelihood of infection needs to be considered when results are negative. Isolation and retesting a few days after a negative result are recommended if some Covid-like symptoms are present, or there has been known or likely exposure to an infected person.

Rapid diagnostic tests are not generally useful within 2 days of being infected. The paper was published in the New England Journal of Medicine.

Hospitalisations of young people with Covid-19  

A US study of just over 3,000 young people (< 18 years old) who visited hospitals with SARS-CoV-2 infections found that 23% required hospital care, and 3% developed severe Covid-19 within two weeks of diagnosis. Four children died from Covid-19.

The risk of developing severe Covid in these young people was greater for those older than five, those with a pre-existing chronic illness or previous case of pneumonia, and those who came to hospital 4 to 7 days after symptom onset.

The study was based on young people with Covid-19 visiting hospitals, so overestimates the risks of hospitalisation, since many infected young people do not need to go to hospital. The paper was published in JAMA Network Open.

Developmental effects of the pandemic on young children

A news item in Nature discusses research into brain development and behaviour in children born during the pandemic. For some, particularly in lower income families, development appears to be lagging for both infected and uninfected children.

A variety of factors may contribute to this, and specific causes have not been confidently established. At least some of the delays in development are expected to be temporary, but some long term developmental implications are still uncertain.

Immune responses to infection

A detailed look at the immunological pathways associated with Covid-19 was published in Science Immunology.

Models to predict risk of new mutations

A model predicts what mutations are likely to appear in the spike protein in variants over the next few months. The model was found to be quite accurate when used to predict the mutations occurring in previous variants. It does not predict what the public health consequences of the mutations will be. The paper was published in Science Translational Medicine.

Another model assesses variants for immune escape and receptor binding ability. The model is based on sequence data, modelling of spike protein structures, and artificial intelligence. Predictions were tested in laboratory experiments. The model was found to provide an often effective early warning system for variants of interest.

Between September 2020 and November 2021 new variants were screened using the model. Twelve of 13 variants subsequently listed as potentially dangerous by the WHO were identified as high risk by the model on average two months before the WHO made their declarations.

The Omicron variant, because of its large number of mutations, was identified as a risk the day its genome sequence was added to the genome database. However, the model did not identify the Delta variant (and related variants) as a high risk. This is because the model does not include every mutation to determine immune escape and infectivity, and because few Delta genome sequences were available before it spread out of India. The paper has not yet been peer reviewed.

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