Coronavirus Research Tracking - 22 April
Vaccine effectiveness in children, 3 dose effectiveness in adults, long Covid, monoclonal antibody therapies
This week, vaccine effectiveness in children, and why three doses can give greater protection in adults. Plus, how fitness trackers could help identify subtle changes after vaccination.
In non-vaccine papers, long Covid prevalence, game theory applied to mask wearing, promising monoclonal antibody treatments, possibilities for a universal coronavirus drug, and evolution of variants.
The tracker is shared with the COVID-19 Vaccine Media Hub.
The Research Tracker is prepared by Dr Robert Hickson for the Science Media Centre.
Vaccines effective in reducing hospitalisations in children
Hospitalisation rates of unvaccinated 5-to-11 year olds were about twice as high as vaccinated children in the US. Those with diabetes or obesity were most likely to develop severe Covid-19.
Omicron was the dominant variant at the time of the study. Not all Covid-related hospitalisations may have been identified. The paper was published in Morbidity and Mortality Weekly Report.
Significant decline in antibodies 3-to-6 months after second Pfizer dose
There is a significant decline in antibody response between three and six months after receiving a second Pfizer/BioNTech vaccine dose. However, it is unsure if this correlates with waning immunity.
Compared to those with natural infections, very low levels of IgM antibodies were produced after vaccination. The study tested serum samples from 15 health care workers over six months. The paper was published in PLoS ONE.
Three vaccine doses better than two against BA.2
A Swedish study found that vaccine effectiveness against severe Covid from BA.1 and BA.2 was similar after three Pfizer doses, but declined in those who had only two. This was assumed to be due to better immune evasion by BA.2.
The protection offered by a prior infection also declined when the BA.2 subvariant dominated. The paper has not yet been peer reviewed.
Third mRNA dose creates more potent antibodies
A third vaccine dose creates a more diverse set of memory B cells than seen after two doses. Antibodies produced from this expanded memory B cell population have more potency and breadth of binding than those from just two doses. The antibodies produced after the third dose appear to target more conserved regions of the spike protein receptor binding domain.
This can help explain why three doses are better able to provide protection against severe Covid. The study is based on a longitudinal study of 42 people. The paper was published in Nature.
Fitness trackers may help monitor subtle reactions to vaccines
Smartwatches and fitness bands may be able to detect subtle reactions to vaccines. In most individuals in this study their resting heart rate increased relative to their individual baseline after vaccination, peaked on day 2, and returned to normal within six days of vaccination. Normal daily and sleep patterns were not affected.
The differences were small, and only one standard deviation higher in 47% of the people. However, the authors suggest smartwatches and fitness trackers could be a simple useful means to help determine immune responses to vaccines (though the study doesn’t measure antibody or T cell levels).
5,600 people provided readings for the study. They had received the Moderna vaccine. The paper was published in npj Digital Medicine.
Omicron more transmissible than earlier variants in a primary school
A Swiss study found that transmission of Omicron was higher at a primary school than earlier variants. Transmission was found in both students and teachers, even if vaccinated. Most infections were symptomatic, though none required hospitalisation. Infected children subsequently spread the infection to their households.
The study was small, involving only 87 students and staff in four classes who shared some class spaces at one school, and 57 household contacts. Thirty two students and staff tested positive, along with 25 household contacts. It was undertaken over winter and during a period of high levels of community cases. The study did not track who transmitted infections to who within the school. The paper was published in The Lancet Infectious Diseases.
One third of Covid patients may still have some symptoms 3 months later
A study of one thousand patients with Covid-19 found around 30% still had symptoms two to three months later. Fatigue was the most common persistent symptom.
Long Covid was more likely in those who had a history of hospitalisation, and in those with diabetes or who were significantly overweight. Age, ethnicity, and social deprivation were not found to correlate with long Covid. The paper was published in the Journal of General Internal Medicine.
Game theory and mask wearing
Game theory was applied to explore communication and decision making about mask wearing between two people. Taking account of whether each individual is infected or uninfected, and does or doesn’t wear a mask, there are 16 possible strategies. Six of the strategies appear to explain the range of behaviours seen during the pandemic.
The authors note that their paper doesn’t lead to recommendations, but provides a theoretical basis for observed behaviours. The paper has not yet been peer reviewed.
Monoclonal antibody able to neutralise a broad range of coronaviruses
A human monoclonal antibody has been identified that could be able to provide protection against a range of coronaviruses. The antibody, and two others with similar breadth of binding, was isolated from a Covid-19 patient.
It was able to neutralise or bind to the Spike protein from a range of variants, other human and animal coronaviruses. The antibody also provided protection to mice infected with SARS-CoV-2.
A common set of amino acids were found in the spike proteins it bound to, which could inform the development of a general vaccine, or broad spectrum treatment. The paper was published in Science Translational Medicine.
Double antibody treatment very effective in preventing infections in clinical trial
A clinical trial of a two antibody combination found that it could be used as a prophylaxis. A single dose injected into muscle reduced symptomatic infections by 77%, with a relative reduction in risk of 83% over six months. None of those receiving the treatment developed severe Covid, while several receiving the placebo did. There were no significant adverse events reported from the treatment.
The neutralising activity of the two monoclonal antibodies appears to be only slightly lower against the BA.2 subvariant than the wild-type virus. The trial involved more than 5,000 participants.
A limitation in the study is that infection rates were low in both those who received the antibodies and in those who had the placebo. The paper was published in the New England Journal of Medicine.
Key viral protein structure determined, and could help create a universal coronavirus drug
The structure of the main protease in SARS-CoV-2 has been determined. The protein, which plays a role in processing the viral proteins, is highly conserved across coronaviruses, so it is a very attractive target for drugs that disrupt it. Understanding the structure helps identify, and design, potential inhibitors of the protein. The paper was published in Proceedings of the National Academy of Sciences.
Identifying previous infections from antibodies in saliva
Saliva samples can potentially be used to detect recent infections by measuring antibodies. Greater reliability was found when the results from several different types of Enzyme-Linked Immunosorbent Assays were used.
Detecting antibodies in saliva could provide an early warning of infection when PCR tests are not readily available. Further research is needed to improve collection methodologies to ensure consistent results, and to determine whether non-ELISA tests can provide greater diagnostic accuracy. The paper has not yet been peer reviewed.
Antigenic drifts and shifts in variants
A detailed review of viral variants compares transmissibility and immune evasion. It reports that the Omicron variant marked a change from antigenic “drift” seen in earlier variants to a larger antigenic “shift”. The authors suggest that the virus still has the potential for further evolution and new impacts. The paper was published in Perspectives in Medicine.