Coronavirus Research Tracking - 8 July
Vaccine effectiveness, pan-coronavirus vaccine, immune system dampening, post-pandemic behaviours, BA.2.75
This week, more studies of vaccine effectiveness in the elderly, overweight, and immunocompromised, as well as a possible reduction in long Covid risks. And more new vaccines in development.
Another study indicating pre-Omicron infections can dampen the immune response to Omicron. And, we may not completely say goodbye to masks and physical distancing after the pandemic.
The Research Tracker is prepared by Dr Robert Hickson for the Science Media Centre.
Note: there will be no Tracker next week.
Vaccine-related papers
Three vaccine doses maintain vaccine effectiveness in the elderly
In Finland three Pfizer doses maintained strong protection against severe Covid in the elderly, even for Omicron. The study involved nearly 90,000 people over 70 years old. Vaccine effectiveness against hospitalisation three to six months after a second dose was 85%. After a third dose, effectiveness increased to 95% over the following two months. Effectiveness against requiring intensive care remained high, with less waning after the second dose.
Results for the Moderna vaccine were not significantly different, but the effectiveness of the AstraZeneca vaccine was slightly lower. The study included infections between January and March 2022, when the Omicron variant was dominant. The paper has not yet been peer reviewed.
Vaccines provide good protection for overweight and obese adults
A study involving the health data of 9 million adults in England concluded that two vaccine doses provided good protection against severe disease in those who were overweight or obese, compared with a similar unvaccinated group. However, when comparing vaccinated groups the risk of severe Covid was higher (after 2 vaccine doses) for underweight and obese adults than for those with a healthy weight.
The study recommends better targeting of vaccination programmes to low weight people, who have a lower rate of vaccination than other weight categories. Some individuals’ BMI measurements were not recent, and BMI can fluctuate or be imprecise, which may have small effects on the results. The Pfizer, Moderna and AstraZeneca vaccines were included in the study. The paper was published in The Lancet Diabetes & Endocrinology.
Modelling vaccine effectiveness in immunocompromised people
A mathematical model suggests that a series of booster vaccine doses may be needed for immunocompromised people. This study modelled the effects of different variants and different vaccines. The model accurately predicted antibody responses to an infection, as well as waning immunity after vaccinations. The paper has not yet been peer reviewed.
Risk of long Covid could be considerably lower after vaccination
A short article, published in JAMA, found that two or three Pfizer vaccine doses, as well as being male, were associated with a lower risk of developing long Covid. In unvaccinated people, the prevalence of long Covid was 48%, while for adults with two or three vaccine doses the prevalence was 16-to-17%. The risk of developing long Covid after 3 doses was calculated to be 84% lower than for an unvaccinated female.
None of the participants with Covid-19 were hospitalised. Symptoms were self-reported. The study was relatively small, involving 265 vaccinated people. The latter may contribute to the greater risk reduction reported in this study, compared with other studies.
Vaccine effectiveness against Omicron may improve with a longer gap between second and third doses
A longer gap between the second and third vaccine doses may improve antibody responses to Omicron variants. This is the conclusion for a study involving two inactivated virus vaccines (CoronaVac and BBIBP-CorV) and a protein subunit vaccine.
For a 4-to-6 month interval, neutralising antibody titres were 10-fold higher against the wild type virus and 30-fold higher against Omicron variants, compared to a one month interval. Antibody responses to Omicron variants were still lower than against the wild type. Only small numbers of participants were involved in each vaccine interval group. The paper was published in the New England Journal of Medicine.
Promising early tests of a broad spectrum coronavirus vaccine
Nanoparticles with eight different coronavirus receptor binding domains (RBDs) may provide broad protection against coronaviruses. When tested on mice and macaques, immune responses were greater for the nanoparticles with eight different RBDs than particles with only a single SARS-CoV-2 RBD.
The former were able to reduce viral loads and infection symptoms even against SARS-CoV-2 variants whose RBDs were not on the particles. Only small numbers of animals were used in the experiments. The paper was published in Science.
Another inhalable vaccine being tested
An inhalable Covid vaccine produced promising results in mice and hamsters. Good humoral and cellular immunity was generated, and reduced lung damage in the hamsters. The vaccine can be stored at room temperature. However, producing it is technically challenging. The paper was published in Nature Biomedical Engineering.
Non-vaccine-related papers
Prior infections can damp the immune response to Omicron
Immune responses to an Omicron infection can be weaker in people with earlier wild type or Alpha variant infections. This is attributed to immune imprinting, and affected both antibody and T cell responses.
This study involved triple vaccinated health care workers, and the authors introduce a new term “hybrid-immune-damping” to characterise their observations. The paper was published in Science.
Post-pandemic we may maintain some physical distancing
A viewpoint, published in Science, suggests that modest reductions in physical contact may persist. Mask wearing in certain settings (such as on public transport) may remain relatively common, physical touching could be reduced, and workplaces are becoming less densely populated. These shifts may have substantial impacts on a range of endemic infectious diseases. Transmission is expected to decrease, although for some diseases a rise in cases may initially occur due to a greater number of susceptible individuals.
The article notes that disease surveillance systems should change. More attention needs, the author states, to be paid to human behaviour and pathogen genomics, rather than just counting cases.
The BA.2.75 variant
Information on the more recent BA.2.75 variant is provided in a Twitter thread. It’s suite of mutations is causing some concern, but there is as yet limited information on its transmissibility, pathogenicity and immune evasion abilities.