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COVID-19 candidate vaccines


There is a large global effort to develop vaccines for protection against COVID-19 and at least 19 vaccine candidates have, as of 31 July 2020, entered clinical trials, including phase 2 and 3 trials.

Established and new vaccine production technologies are being used for development of COVID-19 vaccine candidates: whole-inactivated virus, live attenuated virus, protein subunit, replicating and non-replicating viral vectors expressing SARS-CoV-2 proteins as well as DNA and RNA technologies delivering gene sequences that encode SARS-CoV-2 proteins that then are produced by host cells.

Safety and immunogenicity data have been reported in the scientific literature for phase 1 trials assessing a vector-based SARS-CoV-2 vaccine candidate conducted in China and a mRNA SARS-CoV-2 vaccine candidate conducted in the US.

Further, results from a phase 1/2, single-blind, randomised controlled trial ( The Lancet 2020 ) in five trial sites in the UK of a chimpanzee adenovirus-vectored vaccine ( ChAdOx1 nCoV-19 ) expressing the SARS-CoV-2 spike protein compared with a meningococcal conjugate vaccine ( MenACWY ) as control have been reported.
Healthy adults aged 18–55 years with no history of laboratory-confirmed SARS-CoV-2 infection or of COVID-19-like symptoms were randomly assigned ( 1:1 ) to receive ChAdOx1 nCoV-19 at a dose of 5 × 1010 viral particles or MenACWY as a single intramuscular injection.
There were no serious adverse events related to ChAdOx1 nCoV-19.
In the ChAdOx1 nCoV-19 group, spike-specific T-cell responses peaked on day 14 Anti-spike IgG responses rose by day 28 , and were boosted following a second dose.
Neutralising antibody responses against SARS-CoV-2 were detected in 32 ( 91% ) of 35 participants after a single dose. After a booster dose, all participants had neutralising activity.

EMA ( European Medicines Agency ) has been, as of 30 July 2020, in discussion with developers of 38 potential COVID-19 vaccines.
However, the EMA estimates that it might take at least until the beginning of 2021 before a vaccine against COVID-19 is ready for approval and available in sufficient quantities to enable widespread use in the European Union ( EU ) / European Economic Area ( EEA ).

The opportunities and challenges of developing vaccines against COVID-19 are discussed widely and important lessons from SARS-CoV-1 vaccine development may guide SARS-CoV-2 vaccine design, testing, and implementation.
A major challenge during rapid development is to avoid safety issues. A syndrome of disease enhancement has been reported in the past for a few viral vaccines where those immunized suffered increased severity of infection or death when they later encountered the virus.
Since some SARS-CoV-1 vaccines have shown evidence of disease enhancement in some animal models, this is a concern for SARS-CoV-2 vaccines. ( Xagena )

Source: European Centre for Disease Prevention and Control ( ECDC ), 2020

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