To get a better idea of the effectiveness of the vaccine against the new strains, perhaps they should calculate its *prevalence*. This was done in a study in Israel and the surprising result was in Israel you are 8 times more likely to be infected with the South African variant when you are vaccinated compared to not being vaccinated:
Israeli data shows South African variant able to ‘break through’ Pfizer vaccine.
Strain is more effective than original COVID and the British variant at bypassing the shot, Israeli scientists find, in first-of-its-kind, real-world study.
By NATHAN JEFFAY
10 April 2021, 8:08 pm 17
<i>In their study, the prevalence of the South African strain among vaccinated individuals who were infected despite their inoculation was eight times higher than its prevalence in the unvaccinated infected population. Though the number of such infections among the vaccinated was relatively small, the findings indicated that this variant was far more successful in getting through vaccinated individuals’ defenses than other strains.
…
In Israel, the massive spread of the extra-contagious British variant starting in early January — to the point that it now accounts for more than 90% of COVID cases — is believed to have been responsible for a major wave in the first months of the year, slowing the exit from the pandemic.
But Stern said it may well have had a silver lining: In the battle between variants, the British is far stronger, and may well be keeping the South African at bay.
“It is possible that the extensive spread of the British variant is blocking the spread of the South African variant,” she said. “Because it spread so effectively, it basically didn’t allow the South African variant to spread — it won the competition.”</i>
Note by calculating *prevalence* this takes into account the different numbers of vaccinated and unvaccinated people, rather than just stating how much each group takes up in the total.
This could be done in regards to fatalities also. You would calculate what is the proportion of the vaccinated of those dying from a particular variant compared to the proportion in the unvaccinated. Since the fatalities would likely be low you could give the numbers in the form of, say, “per hundred thousand” in each group.
Two suggestions for considerations to include in your future risk-benefit analysis.
1) The impact of the second dose of the vaccine must consider not only the effect on strength of immunity but also the effect on the duration of immunity. It is generally thought that the second dose will greatly increase the duration, due to the behavior of memory B cells. It might be too soon to get any actual data on this for the SARS-CoV-2 vaccines, but maybe something can be extrapolated from the behavior of other vaccines.
2) There is a huge externality that accounts for the difference between individual risk and societal risk, namely the fact that at the individual level we discount the effect on others of our own infection. Getting vaccinated imposes some risk on yourself but none on others, whereas failure to do so increases not only the risk of you getting infected, and any accompanying harm to yourself, but also the risk of infecting others. When one person infects another, it is not clear exactly how to apportion responsibility between the infector and the infectee, but certainly the infector bears at least some responsibility in at least some circumstances, as well as some responsibility for the chain of downstream infections. One might, for example, assign equal responsibility to everyone in any chain of infections. The risk-benefit analysis must then consider not only the risk to oneself but the risk to others.
The apparent lower case fatality rate for the delta variant is probably due to demographic differences rather than any difference in the severity of the virus. The data you are showing are for the period Feb 1 to June 14, 2021. The alpha variant was dominant until mid-May, and cases in the UK were declining rapidly in that period, so most of the alpha cases were in February and March. In contrast, nearly all of the delta cases were in May and June. Due to vaccination of the elderly population in the winter and early spring, cases in May and June were among a much younger population than the earlier ones. Since death from COVID-19 is highly concentrated among the very elderly, this demographic difference would result in a much lower case fatality rate for recent cases than for earlier ones, even with no change in the virus itself.
A paper analyzing severity of the delta variant in Scotland over the period April 1 to June 6 found exactly this effect: it looked like the alpha variant led to more severe disease than delta when you just counted hospitalizations among cases, but delta was more severe than alpha after correcting for age and other factors. "In summary, we show that the Delta VOC in Scotland was found mainly in younger, more affluent groups. Risk of COVID-19 hospital admission was approximately doubled in those with the Delta VOC when compared to the Alpha VOC [after correcting for age etc]." https://doi.org/10.1016/S0140-6736(21)01358-1
To get a better idea of the effectiveness of the vaccine against the new strains, perhaps they should calculate its *prevalence*. This was done in a study in Israel and the surprising result was in Israel you are 8 times more likely to be infected with the South African variant when you are vaccinated compared to not being vaccinated:
Israeli data shows South African variant able to ‘break through’ Pfizer vaccine.
Strain is more effective than original COVID and the British variant at bypassing the shot, Israeli scientists find, in first-of-its-kind, real-world study.
By NATHAN JEFFAY
10 April 2021, 8:08 pm 17
<i>In their study, the prevalence of the South African strain among vaccinated individuals who were infected despite their inoculation was eight times higher than its prevalence in the unvaccinated infected population. Though the number of such infections among the vaccinated was relatively small, the findings indicated that this variant was far more successful in getting through vaccinated individuals’ defenses than other strains.
…
In Israel, the massive spread of the extra-contagious British variant starting in early January — to the point that it now accounts for more than 90% of COVID cases — is believed to have been responsible for a major wave in the first months of the year, slowing the exit from the pandemic.
But Stern said it may well have had a silver lining: In the battle between variants, the British is far stronger, and may well be keeping the South African at bay.
“It is possible that the extensive spread of the British variant is blocking the spread of the South African variant,” she said. “Because it spread so effectively, it basically didn’t allow the South African variant to spread — it won the competition.”</i>
https://www.timesofisrael.com/real-world-israeli-data-shows-south-african-variant-better-at-bypassing-vaccine/
Note by calculating *prevalence* this takes into account the different numbers of vaccinated and unvaccinated people, rather than just stating how much each group takes up in the total.
This could be done in regards to fatalities also. You would calculate what is the proportion of the vaccinated of those dying from a particular variant compared to the proportion in the unvaccinated. Since the fatalities would likely be low you could give the numbers in the form of, say, “per hundred thousand” in each group.
Robert Clark
Two suggestions for considerations to include in your future risk-benefit analysis.
1) The impact of the second dose of the vaccine must consider not only the effect on strength of immunity but also the effect on the duration of immunity. It is generally thought that the second dose will greatly increase the duration, due to the behavior of memory B cells. It might be too soon to get any actual data on this for the SARS-CoV-2 vaccines, but maybe something can be extrapolated from the behavior of other vaccines.
2) There is a huge externality that accounts for the difference between individual risk and societal risk, namely the fact that at the individual level we discount the effect on others of our own infection. Getting vaccinated imposes some risk on yourself but none on others, whereas failure to do so increases not only the risk of you getting infected, and any accompanying harm to yourself, but also the risk of infecting others. When one person infects another, it is not clear exactly how to apportion responsibility between the infector and the infectee, but certainly the infector bears at least some responsibility in at least some circumstances, as well as some responsibility for the chain of downstream infections. One might, for example, assign equal responsibility to everyone in any chain of infections. The risk-benefit analysis must then consider not only the risk to oneself but the risk to others.
The apparent lower case fatality rate for the delta variant is probably due to demographic differences rather than any difference in the severity of the virus. The data you are showing are for the period Feb 1 to June 14, 2021. The alpha variant was dominant until mid-May, and cases in the UK were declining rapidly in that period, so most of the alpha cases were in February and March. In contrast, nearly all of the delta cases were in May and June. Due to vaccination of the elderly population in the winter and early spring, cases in May and June were among a much younger population than the earlier ones. Since death from COVID-19 is highly concentrated among the very elderly, this demographic difference would result in a much lower case fatality rate for recent cases than for earlier ones, even with no change in the virus itself.
A paper analyzing severity of the delta variant in Scotland over the period April 1 to June 6 found exactly this effect: it looked like the alpha variant led to more severe disease than delta when you just counted hospitalizations among cases, but delta was more severe than alpha after correcting for age and other factors. "In summary, we show that the Delta VOC in Scotland was found mainly in younger, more affluent groups. Risk of COVID-19 hospital admission was approximately doubled in those with the Delta VOC when compared to the Alpha VOC [after correcting for age etc]." https://doi.org/10.1016/S0140-6736(21)01358-1