Coronavirus Research Tracking - 14 October
Vaccination & long Covid risk, nasal vaccine trial, long Covid prevalence, mask effectiveness against different variants, and lying about adherence to rules
This week in vaccine research, vaccinations reduce risk of long Covid, a third mRNA dose provides good protection against dying from Covid, and a nasal delivery form of the AstraZeneca vaccine disappoints.
In non-vaccine research, the prevalence and persistence of long Covid symptoms, differences in symptoms between Omicron and pre-Omicron variants, the changing effectiveness of masks over time, and (unsurprisingly) people may lie about adhering to public health measures.
The Research Tracker is prepared by Dr Robert Hickson for the Science Media Centre.
Vaccine-related papers
Vaccination can reduce the risk of developing long Covid
A large US study estimated that vaccination before an infection reduced the risk of long Covid by 30-40%. The study involved participants who were more likely to seek healthcare, or were hospitalised. Differences between vaccines were not studied. The paper has not yet been peer reviewed.
A Danish study found that the risk of having long Covid symptoms four months after an Omicron infection was lower in people who had three rather than two vaccine doses. The Pfizer/BioNTech vaccine was the most commonly used in Denmark. The risk of long Covid symptoms was also generally lower for those infected with an Omicron variant (up to January 2022) than for the Delta variant. Results were based on self-reporting in a survey. The paper has not yet been peer reviewed.
A third mRNA dose can be more effective at reducing the risk of death than of hospitalisation
A third mRNA dose was found to be very effective in preventing death, and moderately effective in preventing infection and hospitalisation in the four months after vaccination. Effectiveness against death was 79%, while effectiveness against hospitalisation was 53%, and 42% against infection.
No significant differences were found in effectiveness between the Pfizer and Moderna vaccines. The study is based on data from US Veteran Affairs patients. The third dose was given at least five months after the first dose. Participants were mainly older white males. The paper was published in Annals of Internal Medicine.
Nasal form of AstraZeneca vaccine does not appear to be very effective
A Phase 1 clinical trial of a nasal version of the AstraZeneca/Oxford vaccine did not produce encouraging results. Systemic immune responses were weaker than for the original intramuscular vaccine, and mucosal immune responses were variable and weak. Four participants who received the intranasal vaccine became infected during the 16 week study period.
Thirty previously unvaccinated adults (median age around 34) were given one or two doses of the nasal vaccine. The nasal vaccine did not produce serious adverse effects. The paper was published in eBioMedicine.
Predicting the next variant
An algorithm that looks at the pattern of 10 key amino acid changes in the virus may help anticipate future variants. As with influenza, this knowledge may help inform vaccine design ahead of a seasonal infection wave. The paper was published in Communications Biology.
Non-vaccine-related papers
Long Covid prevalence
A study estimated that about 6% of people globally may have clusters of Covid symptoms that persist for at least three months after a symptomatic infection. The analysis involved a review of published studies and modelling. Three clusters of symptoms were examined - persistent fatigue with bodily pain or mood swings, ongoing respiratory problems, and cognitive issues.
In the published studies, long Covid was more common in women (66% of cases). Modelling indicated that long Covid symptoms were most likely to occur in women over 20 and those who were hospitalised due to or with Covid. However, the pattern of long Covid symptoms differed between women and hospitalised patients.
This 6% estimate is lower than those in many studies due to correction for over-reporting and taking account of pre-Covid health status. The confidence interval around the estimate is, however, broad. The paper discusses a range of limitations in comparing studies. The paper was published in JAMA.
Long Covid symptoms can persist for a long time in some groups
A large Scottish study found that 18 months after a symptomatic infection 6% of people had not recovered, and 42% had partially recovered. Several factors were associated with persistent symptoms, including being hospitalised, older age, being female, socioeconomic deprivation, and having comorbidities.
Vaccination was associated with a lower risk of seven Covid symptoms (loss of the sense of smell or taste, problems with hearing or balance, poor appetite, difficulty concentrating, and anxiety or depression). The study included 31,000 people with symptomatic infections. Symptoms and vaccination status were self-reported. The paper was published in Nature Communications.
Omicron infections can generate different symptoms than earlier variants
Upper respiratory infections were more common after BA.1 infections than pre-Omicron ones. Fever was a less common symptom in those with Omicron. The authors attribute the difference in symptoms to a combination of greater population immunity during Omicron (due to prior infection &/or vaccination), and changes in the virus.
Eighty percent of symptomatic BA.1 cases had positive RAT results five days after symptom onset, and 35% were still positive after 10 days. Nearly 50% of asymptomatic cases also had positive results five days after their initial test, and 19% were still positive after 10 days.
Sixty three thousand children and adults from a San Francisco community testing station were included in the study. The paper was published in JAMA Network Open.
Two prior infections may provide greater protection against more recent Omicron variants, in unvaccinated people
A Qatari study found that having two prior infections reduced the risk of a later Omicron infection. People who had a pre-Omicron infection and later a BA.1 or BA.2 one were less likely to be infected with BA.4/BA.5 than those who only had a prior Omicron infection.
The authors suggest that the pre-Omicron infection probably broadened the immune response, compared with an Omicron infection. Study participants were not vaccinated, and more than half were under 20. (Over 90% of the adult Qatari population is vaccinated.) The paper was published in the New England Journal of Medicine.
Illustrating the immune system battle
Science magazine has an illustrated feature describing how our immune system responds to a SARS-CoV-2 infection, and viral responses.
The protective benefits mask may have varied for different variants
A US study found that the level of protection a mask provided against infection decreased when Omicron variants started to dominate. The results are based on daily reporting of mask use by nearly 40,000 adults.
Before the Delta wave there was a 66% higher risk of infection amongst those reporting not wearing a mask for one or more days. During Delta the risk was 53% higher, while during the early Omicron waves the risk was only 16% higher. A variety of factors may contribute to lower effectiveness during the Omicron wave; such as higher levels of infection, greater transmissibility, waning immunity, and changes in behaviours.
The survey did not ask about type of mask, how long it was worn, or how well the mask fit. Participants self-selected and the study relied on self-reporting, so the results may not be generalisable. The paper was published in the American Journal of Infection Control.
Daily RATs may reduce the need for close contacts to self-isolate
A randomised trial found that daily lateral flow tests (AKA rapid antigen tests) of close contacts of an infected person could reduce the need for self-isolation. Daily testing required swabbing both the nose and throat. Participants who were given lateral flow tests reported that they limited their contact with others and remained cautious. However, many of them were able to work from home, which probably contributed.
This English trial involved over 20,000 adults who took lateral flow tests, and 20,000 who self-isolated. Daily test results were self-reported. Different lateral flow/rapid antigen tests can have different levels of sensitivity, which will affect the effectiveness of this strategy. The paper was published in The Lancet Respiratory Medicine.
In the US many people may mislead about their public health precautions, or just ignore ignore directives
A small national survey in the US found that 42% had lied about or not adhered to Covid public health measures. The main reason for their behaviour was “wanting life to feel normal and wanting to exercise personal freedom.” Types of misrepresentation or avoidance included overstating adherence to public health measures, not mentioning they had symptoms, failing to get tested when they had symptoms, and not self-isolating.
Those under 60 were more likely to misrepresent their adherence to the rules or guidelines, or to not adhere to them. Those who were less trusting of science were also more likely to not comply with requirements.
The results are based on responses from 1,733 adults. Actual levels of nonconformism may be greater if participants are more likely to report what they thought would be more socially acceptable. The survey did not ask about frequency of misleading or nonconformism. The survey is not representative of the whole population. The paper was published in JAMA Network Open.