Coronavirus Research Tracking - 5 August
Moderna vs Pfizer effectiveness, long Covid, symptom resurgence, mask effectiveness, BA.2.75
This week, comparing the effectiveness of the Moderna and Pfizer vaccines, and a vaccine that may provide protection agains the flu and Covid. In other research, symptom clusters in long Covid cases, cardiovascular risks from Covid-19, symptom rebound, mask effectiveness, and BA.2.75 characteristics.
The Research Tracker is prepared by Dr Robert Hickson for the Science Media Centre.
Vaccine-related papers
Moderna vaccine can be more effective than Pfizer’s
A Moderna vaccine booster (3rd dose) was more effective than the Pfizer vaccine in preventing infection and hospitalisation during the Delta and early Omicron waves. Effectiveness was assessed in the 12 weeks after the booster dose, and various vaccine combinations were assessed.
The Moderna booster reduced infection risk by 8%, and hospitalisation risk by 33%, compared with a Pfizer/BioNTech booster. Risk reduction was greater for Moderna when the first two doses were Pfizer, rather than the AstraZeneca vaccine, supporting the benefit of mixed vaccination. The study included 3 million adults. The paper has not yet been peer reviewed.
In a separate study, higher and more sustained antibody levels were seen in people who had two or three Moderna doses, compared with those who were vaccinated with Pfizer/BioNTech. Antibody levels following Moderna vaccination remained relatively stable until about 20 weeks after the third dose, whereas levels in Pfizer recipients tended to decline steadily following the third dose.
The study involved over 800 adults, whose antibody levels were assessed between 8 and at least 32 weeks after the third dose. It was undertaken during the Omicron wave. The paper has not yet been peer reviewed.
Combined influenza and SARS-CoV-2 vaccine shows promise in animal trial
A combination mRNA vaccine against influenza A and SARS-CoV-2 generated good antibody and T cell responses in mice. The immune responses from the combined vaccine were similar to those generated by the individual influenza and Covid mRNA vaccines. The combination vaccine gave some protection from co-infection with both viruses in mice. Although infection wasn’t prevented, viral loads in the lungs were reduced, as was lung damage. Only small numbers of mice were used. The paper was published in npc Vaccines.
Non-vaccine-related papers
Long Covid symptom clusters
A UK study of nearly half a million adults with Covid-19 identified 62 symptoms associated with long Covid cases. Three major clusters of symptoms were identified when assessed 12 weeks after infection: a broad spectrum of symptoms, including pain, fatigue and rash; mental health and cognitive symptoms; and respiratory symptoms.
The authors suggest that long Covid be reclassified into three distinct case types. Eighty percent of people with long Covid had the first set of symptoms. Some symptoms the study identified have not been commonly associated with long Covid. These include hair loss, reduced libido, erectile dysfunction, and chest pains.
Risk factors with long COVID included younger age, female sex, belonging to an ethnic minority, socioeconomic deprivation, smoking, obesity, and variety of comorbidities. However, this study only included non-hospitalised Covid cases. The paper was published in Nature Medicine.
A review of symptoms from over 300,000 people in the UK Covid Symptoms Study also identified distinct long Covid symptom profiles. Some were variant-independent, while others were associated with particular variants of concern. Four symptom profiles were associated with the wild-type, seven with Alpha, and five with Delta.
Three groups of clustered symptoms were common in long Covid cases. These were central neurological symptoms (such as fatigue, brain fog & depression), cardiorespiratory symptoms (breathing difficulties & chest pain; most common early in the pandemic and unvaccinated people), and systemic & inflammatory symptoms.
Vaccination status did not appear to affect the symptom clustering or duration of symptoms, although this requires further study. Symptoms were self-reported. Only the wild-type, Alpha and Delta variants were covered by the study. The paper has not yet been peer reviewed.
Cardiovascular risks from Covid
A Nature news article looks at the evidence for greater cardiovascular risks after having Covid-19. Risk appears to be greatest for those who were hospitalised with Covid. Different studies provide different levels of increased risk, which can be due to study size and their methods. However, close monitoring of those who have been hospitalised with Covid-19, are older or immunocompromised is recommended by the American College of Cardiology.
Symptom resurgence can be relatively common
Viral resurgence has been reported for some taking the antiviral Paxlovid. However, a rebound in Covid symptoms and viral resurgence were also relatively common in a study of those who hadn’t received antivirals.
A rebound in Covid-19 symptoms, after they began to ease, occurred in 27% of participants. Viral resurgence occurred in 12% of participants in the study, although the increase in viral load lasted only about one day. Less than 2% had both symptom rebound and viral resurgence.
Symptom rebound was associated with being female, having higher nasal viral loads, and more severe symptoms. Viral resurgence was more likely in older participants. Assessments were made five days after people enrolled in the study, or 8 days after symptom onset. Just over 500 people were included, most of whom were unvaccinated. Most infections were before the Omicron outbreak. The paper has not yet been peer reviewed.
Sense of smell and taste usually recovered within two years after Covid-19
In a relatively small study most people who had lost their sense of smell &/or taste after infection recovered them within two years. Of the 119 participants whose sense of smell or taste was affected, 88% recovered it, with a marked improvement between four and eight weeks after symptom onset. After two years, three people’s sense of smell or taste had not improved. Ten percent took more than six months for the disruption of smell or taste to disappear.
After two years, 28% of study participants still had at least one Covid symptom, with fatigue being the most common. The study involved 168 people with relatively mild Covid symptoms, and symptoms were self-reported. The paper was published in JAMA Otolaryngology - Head & Neck Surgery.
Human genetic associations with Covid-19 risks
A review found at least 20 human genome loci that are associated with Covid-19 susceptibility or severity. The paper was published in Nature.
Decoy receptor
A modified ACE2 receptor has been developed into a decoy for SARS-CoV-2 by combining it with an antibody. Using the modified ACE2 receptor increases the affinity for SARS-CoV-2 and makes it effective against the range of variants. Animal trials demonstrate that it can be effective when administered before or after infection. Further development is, though, required, including safety testing. A review of this approach was published in Trends in Pharmacological Sciences.
Reduced risk of infection from mask wearing
A review of 13 studies concluded that mask wearers are less likely to become infected than those without masks. The review calculated the probability of getting Covid-19 was 7% for mask wearers and 52% for the maskless, representing a relative risk of 0.13 for masked people.
The individual studies had relatively small numbers of people, and included both community-based and healthcare facility settings. Differences between mask types and snugness of fit were not taken into account, nor were other types of public health measures. The paper has not yet been peer reviewed.
Another short review also found that mask use was associated with a lower risk of infection, although based on the limitations of the reviewed community studies the evidence was assessed as low to moderate. The paper notes that a large randomised study comparing effectiveness of surgical vs N95 masks has not yet been published. The paper was published in Annals of Internal Medicine.
Omicron subvariants
A study of Omicron variants BA.4 and BA.5 concludes that Omicron BA.4 and BA.5 have evolved both antibody escape and enhanced antagonism of human innate immunity, compared with earlier Omicron variants. This has resulted in improved transmission and possibly reduced protection from severe disease.
Changes outside of, as well as within, the spike protein appear to affect transmission and disease severity. The paper has not yet been peer reviewed.
Another analysis found that the BA.2.75 subvariant is slightly more sensitive to antibody neutralisation than BA.4 or BA.5. Its greater transmissibility appears to be related to stronger binding to the ACE2 receptor.
However, it is unclear yet whether it can outcompete BA.5. And, it is more resistant to the monoclonal antibody betelovimab than the other subvariants. The paper has not yet been peer reviewed.