Neutralizing antibody titres to SARS-CoV-2 Omicron variant and wild-type virus in those with past infection or vaccinated or boosted with mRNA BNT162b2 or inactivated CoronaVac vaccines

Omicron, a novel SARS-CoV-2 variant has emerged and is rapidly becoming the dominant SARS-CoV-2 virus circulating globally. It is important to define reductions in virus neutralizing activity in serum of convalescent or vaccinated individuals to understand potential loss of protection from infection or re-infection. Two doses of BNT162b2 or CoronaVac vaccines provided little 50% plaque reduction neutralization test (PRNT50) antibody immunity against the Omicron variant, even at one-month post vaccination. Booster doses with BNT162b2 in those with two doses of either BNT162b2 or CoronaVac provided acceptable neutralizing immunity against Omicron variant at 1-month post-booster dose. However, three doses of BNT162b2 elicited higher levels of PRNT50 antibody to Omicron variant suggesting longer duration of protection. Convalescent from SARS-CoV-2 infection did not have protective PRNT50 antibody levels to Omicron, but a single dose of BNT162b2 vaccine provided protective immunity. Field vaccine-efficacy studies against Omicron variant against different vaccines are urgently needed.

Immunogenicity and waning immunity from the oral cholera vaccine (Shanchol™) in adults residing in Lukanga Swamps of Zambia

Introduction In cholera endemic areas, the periodicity of cholera outbreaks remains unpredictable, making it difficult to organize preventive efforts. Lack of data on duration of protection conferred by oral cholera vaccines further makes it difficult to determine when to deploy preemptive vaccination. We report on the immunogenicity and waning of immunity to Shanchol™ in Lukanga Swamps. Methods We enrolled a cohort of 223 participants aged between 18 and 65 years old from whom serum samples were collected at baseline, day 28 before administration of the second dose, and consecutively at 6, 12, 24, 30, 36, and 48 months. Vibriocidal antibody titres were measured and expressed as geometric mean titres. Box plots and 95% CI were computed at each visit for both Inaba and Ogawa. Seroconversion was defined as a four fold or greater increase in antibody titres compared to baseline titres. Results Overall, seroconversion against V. cholerae Inaba and Ogawa after 1st dose was 35/134 (26%) and 34/134 (25%) respectively. We observed a statistical difference in seroconversion between the two subgroups of baseline titres (low <80 and high ≥80) for both Inaba (p = 0.02) and Ogawa (p<0.0001). From a baseline of 13.58, anti-Ogawa GMT increased to 21.95 after the first dose, but rapidly waned to 14.52, 13.13, and 12.78 at months 6, 12 and 24 respectively, and then increased to 13.21, 18.67 and 23.65 at months 30, 36 and 48 respectively. A similar trend was observed for anti-Inaba GMT across the same time points. Conclusion We found that Shanchol™ was immunogenic in our study population and that vibriocidal antibodies may not be a good marker for long-term immunity. The observed rise in titres after 36 months suggests natural exposure, and this may be a critical time window opening for natural transmission in an endemic areas. We recommend re-vaccination at this time point in high risk areas.

Reliably Assessing Duration of Protection for COVID-19 Vaccines

Decision-making about booster dosing for COVID-19 vaccine recipients hinges on reliable methods for evaluating the longevity of vaccine protection. We show that modeling of protection as a piecewise linear function of time since vaccination for the log hazard ratio of the vaccine effect provides more reliable estimates of vaccine effectiveness at the end of an observation period and also more reliably detects plateaus in protective effectiveness as compared with the traditional method of estimating a constant vaccine effect over each time period. This approach will be useful for analyzing data pertaining to COVID-19 vaccines and other vaccines where rapid and reliable understanding of vaccine effectiveness over time is desired.

Homogeneous Surrogate Virus Neutralization Assay to Rapidly Assess Neutralization Activity of Anti-SARS-CoV-2 Antibodies

The COVID-19 pandemic triggered the development of numerous diagnostic tools to monitor infection and to determine immune response. Although assays to measure binding antibodies against SARS-CoV-2 are widely available, more specific tests measuring neutralization activities of antibodies are immediately needed to quantify the extent and duration of protection that results from infection or vaccination. We previously developed a ‘Serological Assay based on a Tri-part split-NanoLuc® (SATiN)’ to detect antibodies that bind to the spike (S) protein of SARS-CoV-2. Herein, we expand on our previous work and describe a reconfigured version of the SATiN assay that can measure neutralization activity of antibodies directly from convalescent or vaccinated sera. The sensitivity is comparable to cell-based pseudovirus neutralization assays but with significantly shorter preparation and assay run time. As the assay is modular, we further demonstrate that Neutralization SATiN (Neu-SATiN) enables rapid assessment of the effectiveness of vaccines and level of protection against existing SARS-CoV-2 variants of concern and can therefore be readily adapted for emerging variants.

Investigating Adherence to COVID-19 Vaccination and Serum Antibody Concentration among Hospital Workers—The Experience of an Italian Private Hospital

SARS-CoV-2 transmission has been high, especially among healthcare workers worldwide during the first wave. Vaccination is recognized as the most effective approach to combat the pandemic, but hesitation to get vaccinated represents an obstacle. Another important issue is the duration of protection after administration of the full vaccination cycle. Based on these premises, we conducted a study to evaluate vaccination adherence and the anti-S antibodies levels among hospital workers, from January to March, 2021. To assess adherence, an anonymous questionnaire was used. Anti-S antibody levels were obtained from the monitoring serological sample database. In total, 56.2% of the unvaccinated people did not report a previous infection from COVID-19. Among those who have not been vaccinated, 12.5% showed distrust against the vaccine, 8.3% stated to have received contraindications to the vaccination, and 6.3% did not report any choice. Analyzing anti-S antibody levels, only one person was found to have a value below the lower cut-off, two weeks, and three months after receiving their second dose. One was below the cut-off after two weeks, and then above the same cut-off after three months. The results of our survey should be seen as a stimulus to further sensitize hospital staff to the importance of vaccination and pay attention to anti-S antibody levels monitoring.

COVID-19 Anti-Vaccine Sentiments: Analyses of Comments from Social Media

Purpose: This study analyzed the insights and sentiments of COVID-19 anti-vaccine comments from Instagram feeds and Facebook postings. The sentiments related to the acceptance and effectiveness of the vaccines that were on the verge of being made available to the public. Patients and methods: The qualitative software QSR-NVivo 10 was used to manage, code, and analyse the data. Results: The analyses uncovered several major issues concerning COVID-19 vaccine hesitancy. The production of the COVID-19 vaccine at an unprecedented speed evoked the fear of skipping steps that would compromise vaccine safety. The unknown long-term effects and duration of protection erode confidence in taking the vaccines. There were also persistent concerns with regard to vaccine compositions that could be harmful or contain aborted foetal cells. The rate of COVID-19 death was viewed as low. Many interpreted the 95% effectiveness of the COVID-19 vaccine as insufficient. Preference for immunity gains from having an infection was viewed as more effective. Peer-reviewed publication-based data were favoured as a source of trust in vaccination decision-making. Conclusions: The anti-COVID-19 vaccine sentiments found in this study provide important insights for the formulation of public health messages to instill confidence in the vaccines.

Durability of ChAdOx1 nCov-19 (AZD1222) vaccination in people living with HIV - responses to SARS-CoV-2, variants of concern and circulating coronaviruses

Duration of protection from SARS-CoV-2 infection in people with HIV (PWH) following vaccination is unclear. In a sub-study of the phase 2/3 the COV002 trial (NCT04400838), 54 HIV positive male participants on antiretroviral therapy (undetectable viral loads, CD4+ T cells >350 cells/ul) received two doses of ChAdOx1 nCoV-19 (AZD1222) 4-6 weeks apart and were followed for 6 months. Responses to vaccination were determined by serology (IgG ELISA and MesoScale Discovery (MSD)), neutralisation, ACE-2 inhibition, gamma interferon ELISpot, activation-induced marker (AIM) assay and T cell proliferation. We show that 6 months after vaccination the majority of measurable immune responses were greater than pre-vaccination baseline, but with evidence of a decline in both humoral and cell mediated immunity. There was, however, no significant difference compared to a cohort of HIV-uninfected individuals vaccinated with the same regimen. Responses to the variants of concern were detectable, although were lower than wild type. Pre-existing cross-reactive T cell responses to SARS-CoV-2 spike were associated with greater post-vaccine immunity and correlated with prior exposure to beta coronaviruses. These data support the on-going policy to vaccinate PWH against SARS-CoV-2, and underpin the need for long-term monitoring of responses after vaccination.