Vaccine-related papers

Third Pfizer dose improves protection from Omicron

A third Pfizer/BioNTech dose may substantially boost neutralisation of the Omicron variant. Neutralisation activity after the third dose was similar to that seen for two doses against an early SARS-CoV-2 strain. The decline in neutralisation activity was relatively small up to four months after the third dose.

The experiments were done by inserting the Omicron spike sequence into a Wuhan strain, so the results may not be the same for a real Omicron variant. The paper was published in Cell Host & Microbe.

Hospitalisation rates lower in South Africa in Omicron wave

In South Africa the Omicron infection wave resulted in much lower hospitalisation levels than earlier waves. Infections also fell off more quickly. This is attributed to immune responses generated by previous infections and vaccinations. The paper was published in the New England Journal of Medicine.

A longer gap between first and second mRNA doses can generate a stronger immune response …

A News & Views article in Nature Immunology discusses the results and implications of a study showing stronger antibody responses when there is a longer gap between the first and second Pfizer/BioNTech doses. (The original study was featured in the 4 February Tracker).

It focuses on the uncertainties of the persistence of these higher levels, the need for more information on the impacts on T cells after a longer dose interval, and whether people with a longer dose interval have better protection against Omicron.

In a separate study, a third dose of either mRNA vaccine resulted in a more diverse set of antibody-producing memory B cells. These can produce antibodies that bind to a range of variants, and probably contribute to reduced disease severity rather than preventing infection.

The experiments used pseudovirus versions of variants, so may not produce the same responses as real infections. Serum samples were taken from 8 people who received the Moderna vaccine, and 35 who had the Pfizer/BioNTech. The paper has not yet been peer reviewed.

… but another study doesn’t

A UK study found no difference in the level of protection from infection between a shorter (under 6 weeks) and longer interval (over 6 weeks) between first and second Pfizer/BioNtech doses. This contrasts with the conclusions of other studies. The authors suggest that their result may reflect that they examined all infections, not just symptomatic ones. Though this doesn’t account for observed changes in memory B cells.

The study also reports that unvaccinated people who became infected had good levels of protection from infection for up to a year, compared to an unvaccinated person who had no prior infection.  The risk of infection was between 81% and 89%  lower for the former. After 12 months immunity began to wane. In contrast, vaccination after an infection boosted immunity for infection, and this persisted beyond one year. The paper was published in the New England Journal of Medicine.

Research needed into the factors that influence immune responses

A article published in Nature Immunology suggests that differences in individual immune responses to vaccines needs further research. It is likely, the authors suggest, that age, biological sex, diet, geographical location, microbiome composition and metabolites all influence innate and adaptive responses. A better understanding of these influences could lead to improvements in vaccine design and the adjuvants used in the vaccines. It may also help in the development of a universal coronavirus vaccine.

Cases of multi-system inflammatory syndrome in children after vaccination are rare

A US study found that multi-system inflammatory syndrome in children after vaccination is rare. Only 21 people out of 21 million aged 12-20 who were vaccinated were diagnosed with the condition. Most of the cases also had evidence of SARS-CoV-2 infections. All the cases were hospitalised but eventually discharged.

The study covered people vaccinated in the first 9 months of the vaccination programme, and used the Vaccine Adverse Event Reporting System. The authors note the difficulty in diagnosing multi-system inflammatory syndrome in children, and consider some cases were probably not identified.  The paper was published in The Lancet Child & Adolescent Health.

Strong allergic reactions to both first and second mRNA doses are uncommon

An analysis of 22 studies found that few people who had an allergic reaction to their first mRNA vaccine dose had a severe reaction after their second. The studies looked at reactions within four hours of the injection. Five percent of those who had a severe reaction to the first dose also had a severe reaction to the second. Overall, among 1366 people who had an allergic reaction (from mild to severe) to their first dose only 0.16% had a severe reaction after the second. The paper was published in JAMA Internal Medicine.

Vaccination may reduce Long Covid symptoms

Vaccination was found to be associated with reduced prevalence of long Covid symptoms, compared to unvaccinated people. About one third of vaccinated people surveyed reported the symptoms disappeared or improved.

The study is based on self reporting, and not all potential differences between the people who were vaccinated and those who weren’t could be excluded. Further research is needed to establish a causal relationship between vaccination and long Covid symptoms. The paper was published in the Journal of General Internal Medicine.

Non-vaccine-related papers

BA.2 infection not worse than BA.1 in South Africa or some other countries

A South African study found that the risks of hospitalisation and severe disease following a  BA.2 subvariant infection were about the same as for the BA.1. The paper has not yet been peer reviewed.

The World Health Organisation’s Technical Advisory Group released a statement saying that the BA.2 subvariant should still be considered a sublineage of Omicron. It notes that studies from several countries have not found greater virulence of BA.2 compared to BA.1, at least in previously infected or vaccinated people. However, the statement also notes that more monitoring and research is needed.  

BA.2 can infect soon after a BA.1 infection

A Danish study found that BA.2 infections can occur within two months of a BA.1 infection, but they are rare. Most of these reinfections occurred in young (median age of 15) unvaccinated people, who had a mild earlier infection. Viral loads were usually considerably lower in the reinfection cases.

Out of 1.8 million cases, potential reinfections (not all involving BA.2) between 20 and 60 days were found in only 1,739 cases (around 0.1%). The paper has not yet been peer reviewed.

Vitamins don’t help much

Micronutrient supplements, such as Vitamins C & D and zinc, do not reduce the risk of death from Covid-19, according to a meta-analysis. Vitamin D was, though, associated with a shorter time being intubated and in hospital compared with standard care.

Twenty six studies, involving 5,633 people, were included in the analyses. The authors note that double-blind randomised clinical trials are the best way to determine effectiveness, which was not the case in the studies they evaluated. The paper was published in Clinical Nutrition Espen.

Identifying the mutations to monitor most closely

Computer modelling of mutations seen in different Variants of Concern helped identify the ability of variants to bind to the ACE2 receptor, and to evade antibody binding. The paper suggests that some mutations affecting the furin cleavage site can increase infectivity and virulence, so these mutations need to be monitored closely. The paper was published in iScience.

Wastewater testing plus clinical monitoring make a strong early detection system

A retrospective UK study found that wastewater testing could sometimes detect the Alpha and Delta variants weeks before they were detected clinically. At other sampling sites the variants were detected in wastewater only after clinical discovery. The authors suggest that combining clinical and wastewater monitoring will provide the best way for early detection of new variants.

The authors also note that detecting the transition from one dominant variant to another can initially be missed in wastewater when there are small numbers of infections of the new variant. The paper has not yet been peer reviewed.

Young children can produce fewer aerosols than adults

When breathing, speaking or singing 8-to-10 year olds appear to produce substantially fewer aerosol particles than adults, which could influence the risk of virus transmission. Particle emission and volume rates were both four-fold lower than for adults. However, there can be considerable variation in emission rates, volumes, and particle sizes between individuals.  

The study involved 15 children and 15 adults, none of whom had a SARS-CoV-2 infection. It was undertaken in a controlled laboratory setting, so differences are expected under real conditions. Viral load is also a critical factor in transmission risk, so this study doesn’t prove children will always present a lower risk of transmission.  The paper was published in the Journal of the Royal Society Interface.

Long Covid visual resource

The New York Times has an interactive article describing how long Covid can affect different parts of the body. [A subscription may be required to view it]

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