Once a vaccine had been designed, tried and tested by the scientific community the manufacturing and production of successful vaccines would be another unprecedented challenge to overcome.
Yet, a little over a year since the pandemic began Luxembourg now has 3 vaccines (with another on its way) available to vaccinate its population. 11 vaccines are currently being used globally to protect against Covid-19 infection and severe disease. This underlines just how much progress has been made in vaccine development since last year.
While vaccine development and production continues, the conversation has notably shifted to comparing the available vaccines. Reports on vaccine efficacy and safety are constantly evolving and updated according to new data. So some vaccines have been halted all together or only administered to certain groups in the population, and vaccine strategies have been changed and then changed back again. However, delays caused by changing vaccine strategies leave a significant number of people at risk for Covid-19 infection and associated complications.
One study used mathematical modeling to predict how different vaccine roll-out speeds would impact the number of deaths from Covid-19 infection in Italy. Without any vaccination, it was predicted that 298,000 deaths would occur from April 2021 to Jan 2022. Slow vaccine roll out would reduce the predicted number of deaths to 90,000 (30% of 298,000), whereas fast vaccine roll-out would reduce number of deaths to 51,000 (17% of 298,000).
This means that a fast vaccine roll-out could help prevent as many as 39,000 deaths in Italy, which highlights the importance of speed in vaccine roll-out strategies. However, the success of vaccination programs will of course also depend on vaccine efficacy against different SARS-Cov-2 variants, and vaccine technologies must be able to keep up with the arrival of new variants.
Thousands of SARS-Cov-2 variants have been identified through genomic sequencing. Each variant has a mutation that is a result of a tiny copying error when an infected cell builds new coronaviruses during natural infection. Some mutations will not impact the virus, but sometimes mutations can be harmful limiting viral replication and thus successful infection. For this reason, in-built mechanisms often exist in viruses to control the rate of mutation.
The SARS-Cov-2 virus has a proofreading mechanism during viral replication, which results in a lower mutation rate (about half) compared with the influenza virus. Nevertheless, all viruses will mutate to some degree and sometimes these mutations prove useful to the virus, potentially increasing its ability to infect new cells or to evade existing vaccinations.
Currently there are 6 SARS-Cov-2 mutations that may help the coronavirus spread and 4 variants have been labeled as “Variants of concern”. These include B.1.1.7 discovered in Britain in December 2020 which is reportedly 50% more infectious, and the B.1.351 variant which emerged in South Africa. While vaccines including Vaxzevria (Oxford–AstraZeneca), Pfizer-BioNTech, Moderna and Johnson&Johnson are effective against the B.1.1.7 variant, initial laboratory studies as well as a “real world” study from Israel suggest B.1.351 is evading neutralizing antibodies in some cases both after natural infection with SARS-Cov-2 or after vaccination.
This does not mean current vaccines will not be effective at all with the B.1.351 variant, but might just be less effective compared with other variants. More clarity is needed from ongoing vaccine trials to determine the actual impact each variant has on efficacy of existing vaccines. If needed, mRNA technology may offer the necessary flexibility to quickly adjust vaccines to protect against new variants in the long-term. However, more traditional vaccine technologies should not be overlooked at this stage, as every approved vaccine can contribute to reducing severe disease and deaths associated with Covid-19, particularly while vaccine availability remains limited.
It is important to remember that vaccination does not yet always prevent transmission of the virus. Vaccinated individuals can still test positive for the virus, and could therefore still pass the virus on to others who may not yet be vaccinated. This suggests that non-pharmaceutical interventions such as physical distancing, wearing a mask and restrictions will continue to be needed to slow down the spread of the coronavirus.
In fact, mathematical modeling suggests that implementation of such measures could significantly reduce the number of deaths associated with Covid-19. In Italy, it is predicted that non-pharmaceutical interventions will reduce the predicted number of deaths from 298,000 to 30,000 even without vaccination, and to 18,000 with fast roll out of vaccination. This underlines that a balance of non-pharmaceutical interventions and vaccination programs will be required to manage the Covid-19 pandemic in the long-term.
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Angela Marley, PhD Immunology & Infectious Disease
Nature: modeling vaccination rollouts
Immunity: Lessons for COVID-19 immunity from other coronavirus infections
Nature: The coronavirus is mutating - does it matter?
Bol Med Hosp Infant Mex.: SARS-CoV-2 and influenza: a comparative overview
WHO: Variant analysis of SARS-CoV-2
The Lancet: Efficacy of ChAdOx1 nCoV-19 (AZD1222) vaccine against SARS-CoV-2
NEJM: Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant
NYT: Coronavirus Variants and Mutation
Nature: Sensitivity of infectious SARS-CoV-2 B.1.1.7 and B.1.351 variants to neutralizing antibodies
Pre-print article: Evidence for increased breakthrough rates of SARS-CoV-2 variants of concern in BNT162b2 mRNA vaccinated individuals
