Browsing by Author "Hartshorne, Johan"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item A review of leading COVID-19 vaccines, the quest for immune protection, and its key challenges. Part 3: Covid-19 vaccines – Key challenges and translational science(2021-05-06) Hartshorne, Johan; Villiers, PierreRationale • Developing and deploying safe and effective COVID-19 vaccines are faced with many challenges and unanswered questions. • Massive amounts of heterogenic scientific data are being generated that are needed rapidly to advance vaccine development, protect people and restore normality. • The purpose of Part 3 of this four-part series is to review the scientific considerations related to key challenges associated with COVID-19 vaccines and immune protection with the focus of making this data more meaningful and open for clinicians. Key points • The primary immunogen (antigen) required to induce neutralising antibodies (humoral) and T cell (cellular) immune responses is the S-protein fragment of SARS-CoV-2. • Currently, the evidence is firmly pointing towards neutralising antibodies, being more critical for protection. • Long-term protective or durable immune memory is driven by virus-specific T cell and B cell responses (adaptive immunity). • Circulating antibody titres are not predictive of T cell immune memory. • Durable immune memory is a crucial factor to sustain herd immunity. • Adjuvants are added to certain vaccines to provoke a more robust and durable immune response. • Adjuvants that provoke TH1-biased immune responses are preferred. • 90% of adults are seropositive for 'common cold' CoV strains. • There is a cross-reactivity between specific T cell of SARS-CoV-2 and 'common cold' CoV's. • Prior infection with 'common cold' can play a potentially protective role. • Seropositive individuals present with a rapid and higher antibody immune response after a single dose with an mRNA vaccine. • Vaccine-induced immune responses resulting in non-neutralising antibodies, low antibody titres, and abnormal T cell responses (TH2- biased) are potential risks for serious enhanced disease events but unlikely events. • Vaccine strategies aimed at inducing high titres on neutralising antibodies and TH1- biased immune responses reduce the risk of serious adverse events. • Emerging variants of concern are extremely infectious, highly transmissible and threatens the protective efficacy of current vaccines. Public health implications • A rapid global vaccination campaign combined with standard mitigation measures to stop transmission is the best defence against the emergence of further SARS-CoV-2 variants and the safest way to attain herd immunity. • Booster immunisations may be required to promote or improve the durability and strength of vaccine immunity.Item A review of leading COVID-19 vaccines, the quest for immune protection, and its key challenges. Part 4: Global Covid-19 vaccination campaign – supply and distribution logistical requirements and challenges.(2021-05-06) Hartshorne, Johan; De Villiers, PierreRationale • Rapid manufacturing and effective distribution of sufficient quantities of vaccines is paramount to launch a successful vaccination campaign that will successfully achieve herd immunity to interrupt the pandemic crisis. • The fundamental objective driving COVID-19 vaccine deployment is to ensure that all people have fair access to safe and effective COVID-19 vaccines. • The purpose of Part 4 of this series is to highlight the logistical and ethical challenges of the supply and distribution chain of COVID-19 vaccines. Key points • All phases of the COVID-19 vaccination campaign merits strong consideration from an ethical and logistical perspective. • Vaccines must be authorised by regulatory authorities before use. • Governmental implementation bottlenecks are the cause of the inability to vaccinate at-risk populations rapidly. • Productivity and manufacturing of mRNA-based vaccines remain low, and ultra-cold chain requirements impose significant storage and distribution challenges. • Viral vector-based vaccines are based on proven technology and expected to yield significantly higher annual volumes. • Recombinant protein subunit vaccines can be easily scaled up, are reasonably stable and easier to manage, but development is currently running months behind schedule. • Live attenuated and whole inactivated virus vaccines require regulatory-approved biosafety level 3 (BSL-3) facilities for development and manufacturing, thus have more safety hurdles, are more complicated and slower to develop, and therefore unpredictable to manufacture. • An effective vaccination campaign requires adequate procurement of vaccines and political will. • Health care workers and elderly adults are the highest priorities for vaccination. • Exposing vaccine distribution and implementation plans to scrutiny is critical. • Allocation of limited vaccines should be prioritised and based on the ethical principles of maximising benefits, minimising harms, fair and equal access, transparency, informed consent and trust. • Public trust can only be ensured through transparent communications and consistently applied allocation of safe, effective, and fair vaccines to everyone. • Safety and public trust are critical considerations in vaccine acceptance. • Health care professionals are the most trusted source of information. Public health implications • Access to vaccines for global distribution before the end of 2021 will be a task of unprecedented proportions. • Experts recommend that governments invest in a more expansive and diversified portfolio of vaccines. • Many countries are under-resourced with vulnerable high-risk communities. • Multiple stakeholders are driving a global approach to equitable access. • Public distrust, anti-vaccine messaging, and vaccine hesitancy are a significant concern to vaccine campaign efficacy to contain the pandemic.