A summary of some recent studies on COVID-19 include research that warrants further study to corroborate the findings and that has yet to be certified by peer review, reports Reuters.
Unvaccinated Omicron patients at risk from variants
Infection with the Omicron variant of the coronavirus can significantly improve the immune system’s ability to protect against other variants, but only in people who have been vaccinated, South African researchers have found.
In unvaccinated people, an Omicron infection provides only “limited” protection against reinfection, they reported in the journal Nature. In 39 patients who had Omicron infections – including 15 who had been immunised with vaccines from Pfizer/BioNTech or Johnson & Johnson – the researchers measured the ability of immune cells to neutralise not only Omicron but also earlier variants.
At an average of 23 days after Omicron symptoms started, unvaccinated patients had 2.2-fold lower neutralisation of the first version of the Omicron variant compared to vaccinated people, 4.8-fold lower neutralisation of the second Omicron sublineage, 12-fold lower Delta neutralisation, 9.6-fold lower Beta variant neutralisation, and 17.9-fold lower neutralisation of the original SARS-CoV-2 strain.
The gap in immunity between unvaccinated and vaccinated individuals “is concerning”, the researchers said. “Especially as immunity wanes, unvaccinated individuals post-Omicron infection are likely to have poor cross-protection against existing and possibly emerging SARS-CoV-2 variants,” they added.
“The implication may be that Omicron infection alone is not sufficient for protection and vaccination should be administered even in areas with high prevalence of Omicron infection to protect against other variants.”
Obesity may weaken vaccine protection in the never infected
Severe obesity may weaken the effectiveness of COVID-19 vaccines in those who have never been infected with the coronavirus, according to a small Turkish study.
Among those in the study without previous SARS-CoV-2 infection who had received the Pfizer/BioNTech vaccine, patients with severe obesity had antibody levels more than three times lower than normal-weight individuals.
Among recipients of Sinovac Biotech’s CoronaVac, those with severe obesity and no history of prior infection had antibody levels 27 times lower than normal weight people, according to data that were presented at the European Congress on Obesity in Maastricht, Netherlands. By comparison, in the 70 volunteers with a previous coronavirus infection, antibody levels were similar in people with and without severe obesity.
For the study, researchers had compared immune responses to vaccines in 124 volunteers with severe obesity – defined as a body mass index of 40 or higher – and 166 normal-weight individuals (BMI less than 25). Overall, 130 participants had received two doses of the Pfizer/BioNTech mRNA vaccine and 160 had received two doses of Sinovac's inactivated-virus vaccine.
While two doses of the Pfizer/BioNTech vaccine “may generate significantly more antibodies than CoronaVac in people with severe obesity… further research is needed to determine whether these higher antibody levels provide greater protection against COVID-19”, study leader Volkan Demirhan Yumuk from Istanbul University said.
Different vaccines protect well against severe COVID-19
While the mRNA vaccines from Pfizer/BioNTech and Moderna generate higher antibody levels to protect against SARS-CoV-2 infection, AstraZeneca’s viral-vector-based vaccine provides equivalent protection against hospitalisation and death from COVID-19, according to a review of dozens of studies.
A panel of experts in Southeast Asia reviewed 79 previous studies for a study funded by AstraZeneca. Both types of vaccines showed more than 90% efficacy against hospitalisation and death, the panelists said in a report posted on Research Square ahead of peer review.
“The high level of antibodies formed after the COVID-19 vaccination is often interpreted as the effectiveness of a vaccine. We now understand that while initial antibody response levels can vary across vaccines, their ability to prevent being hospitalised or dying from COVID-19 is equivalent,” said panel member Dr Erlina Burhan, a lung disease specialist at the University of Indonesia.
A spokesperson for the panelists said the findings suggest decision-makers should use any vaccine type that is accessible and optimal for their local situation, and that people who have a choice of vaccine should know that the one they can get quickest is best.
A separate study published in Nature Communications found that while Moderna’s mRNA shots provide slightly more protection against coronavirus infection than the Pfizer/BioNTech vaccine, “there are no differences in vaccine effectiveness for protection against hospitalisation, ICU admission, or death/hospice transfer”.
Effectiveness of SARS-CoV-2 vaccines in people with severe obesity (Open access)
See more from MedicalBrief archives:
Relationship between COVID-19 deaths and morbid obesity — large US analysis
Obesity’s strong link to severe COVID outcomes, especially in under-40s and Black people
Why Omicron doesnʼt need its own custom COVID vaccine
SA-German study shows boosters protect but unlikely to prevent Omicron
Mixing COVID-19 vaccinations gives better immune response — Oxford trial