Vaccine-related papers

Omicron-specific vaccine not more effective in an animal trial

An Omicron-specific vaccine from Moderna was not more effective than their original when tested in macaques. The animals were given two doses of the original mRNA vaccine, and then a third dose (either the same or one designed for Omicron) 41 weeks later.

Antibody levels and neutralising antibody activity in both groups were similar when measured two weeks after the third dose. When the animals were infected with Omicron four weeks after dose 3 both vaccines provided complete protection against lung infection.

Only 8 macaques were used in the trial, and infection dynamics and disease in macaques are not exactly the same as in people, so further research is needed. The paper has not yet been peer reviewed.

Unvaccinated people have considerably higher risks of infection and hospitalisation than triple-dosed people

In Los Angeles the infection and hospitalisation rates from the Omicron variant were considerably higher in unvaccinated people than in those who had three vaccine doses. Infection and hospitalisation rates were 3.6 and 23 times higher. When compared with those who had received two vaccine doses, the rates of infection and hospitalisation for unvaccinated people were 2 and 5.3 times higher, respectively.

The study covered the period between November 2021 and early January 2022, and the health records of over 400,000 adults were analysed. Differences in exposure risks could affect comparisons of unvaccinated and vaccinated groups, and some people may have been hospitalised for conditions not related to Covid-19. The paper was published in the Morbidity and Mortality Weekly Report.

BA.2 Omicron subvariant is more transmissible

A Danish study reports that the BA.2 subvariant of Omicron is more transmissible than the BA.1 version, and has additional immune evasion properties. Unvaccinated people with BA.2 were more likely to infect others than vaccinated people with a BA.2 infection.

Those who had had a third vaccine dose were less likely to become infected with BA.1 or BA.2 than people who had two vaccine doses.  The viral load in unvaccinated people with BA.2 infections were found to be higher than for BA.1, but no difference in viral loads between the subvariants were seen in vaccinated people. The paper has not yet been peer reviewed.

A risk matrix for Delta & Omicron severity with and without vaccination

A Swedish study found that risk of severe Covid-19 was significantly lower for both the Delta and Omicron variants if the infected person was vaccinated.

Hospitalisation rates were much lower for those with the Omicron variant, regardless of vaccination status. Risk of hospitalisation was greater for those over 65, and those with several comorbidities.

The paper has not yet been peer reviewed.

Omicron infections in unvaccinated people don’t produce broad immunity

A study in mice found that unvaccinated animals infected by the Omicron variant do not develop broad cross-reactive immunity against other variants. In contrast, infection with the Delta variant did. An Omicron infection enhances the cross-reactive immunity generated by vaccinations. Consequently, unvaccinated people infected with Omicron may be at greater risk from subsequent SARS-CoV-2 infections than vaccinated people. Only 15 mice were infected with each variant.The paper has not yet been peer reviewed.

Novavax vaccine performs well in Phase 3 trial

A Phase 3 clinical trial of the Novavax vaccine found efficacy against infection was 90.4%, with 100% effectiveness against preventing severe disease. Effectiveness against several variants of concern were similar, but the Alpha variant was the most common during the trial. The trial ended before the Delta and Omicron variants emerged.

Adverse reactions to the vaccine were generally mild to moderate and disappearing quickly. Participants were mostly under 65 years old. The paper was published in the New England Journal of Medicine.

Moderna vaccine substantially reduces viral load

A large study found that the Moderna vaccine led to a 100-fold decrease in viral load on the day of diagnosis. The vaccine also reduced the time that virus was detectable, down from seven to four days. The study was conducted before the Delta variant spread. The paper was published in Nature Medicine.

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Non-vaccine-related papers

Long Covid in young people

Two papers on long Covid in young people were published in The Lancet Child and Adolescent Health.

A Danish study compared nearly 25,000 15-to-18 year olds who had become infected with a matched group who had no evidence of prior infection. Those who had had Covid-19 were more likely to have more sickness-related absences from school or work and have long-lasting symptoms (such as chest pain, trouble breathing, coughs, headaches, sore throats, and dizziness).

However, young people with no previous infection scored worse in quality of life assessments (such as being scared, feeling sad, and having trouble sleeping). The authors suggest that this could be associated with the non-infected adolescents being more cautious and concerned about becoming infected.

The second study, from England, examined physical and mental health three months after infections in 11-to-17 year olds. At the time of testing the symptoms of infected young people were not distinguishable from uninfected ones.

However, three months later a set of symptoms (tiredness, headache, shortness of breath, dizziness, and anosmia) were more common in those who had become infected. The paper notes that long Covid is better distinguished by a set of symptoms rather than just one or two.

There were no differences in the mental health and wellbeing of infected and uninfected participants. In both groups about 40% reported feeling worried, sad or unhappy.

An editorial in Nature discusses the need for more research into long Covid in young people.

Increased cardiac risks after infection

There can be an increased risk of a variety of cardiovascular disorders in adults even if their Covid-19 symptoms did not result in hospitalisation. The risk was greater for those who had more severe Covid-19 (requiring supplemental oxygen). Higher risks were still observed one year after infection.  

The study is based on health records from US Veteran Affairs healthcare providers, so reflects mostly older (mean age 61) white male patients. The paper was published in Nature Medicine. A commentary on the study was published in Science.

Infection can create substantially higher risks of developing a range of health problems

An Australian study reports that SARS-CoV-2 infection substantially increases the risk of several conditions. These include myocarditis and pericarditis, pulmonary embolism, thrombocytopenia & coagulative disorders, acute kidney failure, and acute myocardial infarction. Risks were assessed over the 90 days after an infection. The Incident Rate Ratios ranged from 14.76 higher for myocarditis and pericarditis down to  2.31 for myocardial infarction.

Risks of the different conditions varied over time, with some having an increased risk later after infection. The paper has not yet been peer reviewed.

Seeing the virus during infection

A new imaging method allows coronavirus infection processes to be seen in much greater detail. The distribution of viral RNA and the spike protein, and their structural organisation can be monitored. The technique was used to examine how Remdesivir affects a human coronavirus within cells. The paper was published in Cell Reports Methods.

Survival of variants on surfaces

A Japanese study found that the Omicron, Beta, Gamma and Alpha variants could survive about twice as long on plastics and skin as the original Wuhan strain. The Omicron had the longest survival time on skin - 21 hours, compared with 8.6 hours for the Wuhan strain.  

All the variants could be inactivated using ethanol solutions. It is not known why the Variants of Concern have greater environmental stability. Tests were done in controlled environments, so there is likely to be greater variability under natural conditions. Infectivity after environmental exposure was not tested, so it is unknown if risk of infection from surfaces is greater for the Variants of Concern. The paper has not yet been peer reviewed.

Wearing masks indoors reduces infection risks

A Californian study reports that always wearing a mask indoors in public settings reduces the chance of becoming infected. The overall odds of becoming infected when consistently wearing a mask was around 50% lower than non-mask wearing. N95 & KN95 masks were the most effective, reducing the risk by 83%. However, the effectiveness of a cloth mask in reducing risk was not statistically significant in this study.

The study has several limitations. It relied on people choosing to participate, self-reporting of mask use, and deciding to get Covid tests, so is likely biased towards those who are more cautious or concerned about getting infected. Other behaviours that could affect infection risk were not taken into account. The study occurred before the Omicron variant was common.The paper was published in Morbidity and Mortality Weekly Report.

DIY hacks for masks

The effectiveness of a variety of hacks to improve the fit of face masks was assessed. Seven DIY modifications to surgical and KN95 masks were examined. The use of pantyhose, tape, and rubber bands were found to improve fit. Pantyhose over the mask was judged the most effective, although the type of pantyhose had a significant influence on fit.

However, effectiveness varied considerably between individuals, although only four people were involved in the study. The hacks were also often uncomfortable, and probably could only be used for short periods of time. The paper was published in PLOS One.

Random testing would help reduce under-estimates of infection levels

A news article in Nature recommends random testing as a better approach now to tracking infections. This, it suggests, would provide a more accurate assessment of the number of people with mild or no symptoms. It notes that in the UK random sampling programmes have been successful. However, random testing requires greater resources.

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