Coronavirus Research Tracking - 21 January
3rd dose vaccine effectiveness, Omicron and immune responses, lower risk of long Covid after vaccination, multi-system inflammatory syndrome in children
This week, the effectiveness of three vaccine doses, Omicron’s effect on immune responses and its very high breakthrough infection rate, the reduced risk of long Covid after vaccination, and nocebo effects associated with vaccinations.
Non-vaccine papers discuss the potency of antibody cocktails, how “overnight success” with new therapies is built on years of other scientific progress, under-estimating the Covid death toll, multi-system inflammatory syndrome in children, and the influence of prosocial factors on responses to public health measures.
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.
Vaccine-related papers
Three Pfizer doses provide good effectiveness against severe Covid for at least 4 months
Three doses of the Pfizer/BioNTech vaccine provided 89% effectiveness against hospitalisation for the Omicron variant for up to four months. Effectiveness of two doses against Omicron was 68%.
For both the Delta and Omicron variants the effectiveness of two vaccine doses against less severe Covid-19 waned after three months. A third dose increased effectiveness, but that started to wane for Omicron (but not Delta) after three months as well, and effectiveness was lower than for Delta. Longer term follow-up is required.
Some differences in behaviour or other factors between vaccinated and unvaccinated people could affect some of the results, and prior infections were not recorded. Some visits to hospitals may have been for other conditions rather than specifically for Covid-19, which could overestimate less severe cases of Covid. The paper has not yet been peer reviewed.
Strong cellular immunity against Omicron
T cell responses, stimulated by vaccines or earlier infections, do not appear weaker against the Omicron variant. Interferon-gamma production against Omicron was similar to that against the original strain. Three doses of mRNA vaccines resulted in stronger T cell responses than two doses. The paper has not yet been peer reviewed.
Omicron infection can enhance immunity
Omicron infections can enhance pre-existing immunity generated by vaccines. In unvaccinated people an infection with Omicron does not appear to provide protection against other variants, but it does in vaccinated people. The paper has not yet been peer reviewed.
More potent and durable antibody responses from infection + vaccinations
Antibody responses are more potent, broader and durable following an infection after vaccination, compared with the responses generated by two vaccine doses alone, or an infection without vaccination. The immune response after three doses was similar to the two dose + infection response, indicating greater exposure to the spike protein enhances the antibody response.
The study had small sample sizes, with only 15 people in each group. T cell responses were not investigated. The paper was published in Cell.
Reinfection rate 16 times higher for Omicron than Delta
The UK Office of National Statistics calculated that the risk of reinfection was 16 times higher for the Omicron variant than for earlier in 2020 when Delta dominated. Having a previous infection or one or more vaccine doses was associated with a lower risk of infection than if a person was unvaccinated. However the differences were lower in the last two weeks of 2020 than earlier in 2020, reflecting the enhanced transmissibility of Omicron.
Vaccinations reduce the risk of long Covid
An Israeli study found that vaccinations may reduce the risk of long Covid. The frequency of post-Covid symptoms were reduced by more than 50% after two doses of the Pfizer/BioNTech vaccine. The effect was more common in older people. The reason for this is not yet clear, but may be related to weaker immune systems in the elderly. The paper has not yet been peer reviewed.
Nocebo effect may inflate reports of adverse reactions to vaccines
Adverse reactions to placebos in Covid vaccine trials were relatively common, according to a review of 12 studies. Vaccines resulted in more reported adverse reactions, but over 30% of people receiving a placebo reported adverse reactions (such as headaches and fatigue). This is called a “nocebo”effect.
The authors caution that highlighting headaches and fatigue as vaccine side effects may lead to more nocebo responses. They suggest that also providing information about the nocebo effect could help during vaccination programmes. Only 12 trials were reviewed, and there was considerable variability in results between them. The paper was published in JAMA Network Open.
Non-vaccine-related papers
Antibody cocktail reduces risk of immune evasion
A cocktail of highly potent neutralising antibodies reduces the risk of viral variants evading suppression. The antibodies were created using mice and cells from previously infected people. Such cocktail therapies may be useful in controlling the emergence of more transmissible variants. Further trials are underway. The paper was published in Science.
“Fast” drug development builds on years of earlier research
When you get past the detailed chemistry about the development of the Covid pill Paxlovid in Derek Lowe’s blog, there is a very good summary of how what’s often called fast drug development builds on many years of science. And the luck that is needed to go along with it.
An even more detailed description of the development of Paxlovid is published in C&E News.
Global Covid death toll significantly under-estimated
A Nature news item reports that the global Covid-19 death toll is probably millions higher than reported. The official toll is 5.5 million, but data on excess mortality suggest deaths may be well above 10 million. The article discusses the difficulties in accurately estimating deaths.
Covid-related cardiac problems in children may resolve themselves after a few months
A small study of Multisystem Inflammatory Syndrome in Children that is associated with Covid-19 found that cardiac problems may resolve themselves in most cases within 3-4 months. The study focussed on heart issues not other aspects of the syndrome. Longer term follow-up, and larger groups of patients are required. The paper was published in the Journal of the American Heart Association.
Multisystem Inflammatory Syndrome much more common in unvaccinated children
A French study found that nearly all adolescents (12-18 years) admitted to hospital with Multisystem Inflammatory Syndrome in Children were not vaccinated. Between September and October 2021 107 children were hospitalised with the syndrome. Of these, 33 were in the age group (12-18) who could be vaccinated.
None of the adolescents had had two vaccine doses, 7 had received one vaccine dose, and 26 were unvaccinated. By the end of October 73% of adolescents in France had received two vaccine doses (mostly Pfizer/BioNTech). The paper was published in December in JAMA.
Prosocial factors influence individual pandemic responses
A study in Columbia shows that prosocial pre-dispositions influence individual responses to the pandemic. Prosocial characteristics examined included those related to assessment of social cognition and moral dilemmas. Higher levels of personal distress and empathic concern, and stronger moral judgement, were associated with increased Covid-19 risk perception and impact estimation, and these people were more accepting of quarantine measures.
The authors suggest that public health interventions should take greater account of differences in prosocial tendencies. The study was small, surveying only 413 people, had three times as many female respondents as male, and the results may vary between countries. The paper was published in Humanities and Social Sciences Communications.
National wastewater sampling programmes can provide early warning or prediction of new variants
A nation-wide wastewater sampling programme in Austria was able to assess variant abundance and dynamics, and could be used to predict emerging variants. Screening of wastewater complements more traditional public health surveillance. The paper has not yet been peer reviewed.