Impact of vaccination for one age group
Reduction of cumulative deaths
Compared with the current vaccination strategy, if starting from March 1, 2021, the vaccination coverage rate for only one age group (0–17age group, 18–44 age group, 45–64 age group, 65–74 age group, or 75–100 age group) was gradually increased to 40% by June 1, 2021, then the top three age groups with the greatest reduction in cumulative deaths were 75–100, 65–74 and 45–64 age groups as of June 1, 2021, and the reduced cumulative deaths were 63, 23 and 10, respectively (Figure 2A (a)). However, if the vaccination coverage rate for only one age group was gradually increased to 80% by June 1, 2021, then the top three age groups with the greatest reduction in cumulative deaths were still 75–100, 65–74 and 45–64 age groups as of June 1, 2021, and the corresponding reduced cumulative deaths were 111, 42 and 19, respectively (Figure 2A (c)).
In addition, the increased vaccination coverage rate would lead to an obvious reduction in the cumulative number of deaths in NYC (Fig. 2B (a–c)). Specifically, if starting from March 1, 2021, the vaccination coverage rate in the 75–100 age group was increased up to 40%, 60%, and 80% by June 1, 2021, then through normalization, we obtained the reduced cumulative number of deaths in NYC were 72, 95, and 123 per increased 100,000 vaccinated individuals, respectively. Moreover, from Fig. 2B, we can see that increasing the vaccination coverage rate for middle and elderly age groups would reduce the cumulative number of deaths even more in NYC.
Reduction of cumulative new infections
If we gradually increased the vaccination coverage rate for only one age group (0–17 age group, 18–44 age group, 45–64 age group, 65–74 age group, or 75–100 age group) to 40% by June 1, 2021, then compared with the current vaccination strategy, the top three age groups with the greatest reduction in cumulative new infections were 18–44, 0–17 and 45–64 age groups, and the reduced cumulative new infections were 13463, 12807 and 11073, respectively (Figure 3A (a)). Furthermore, if we gradually increased the vaccination coverage rate for only one age group to 60% by June 1, 2021, then, as of June 1, 2021, the top three age groups with the greatest reduction in cumulative new infections were still 18–44, 0–17 and 45–64 age groups, and the reduced cumulative new infections were 17452, 16628 and 14265, respectively (Figure 3A (b)). In addition, from Figure 3A (c), we can see that the increased vaccination coverage rate would lead to an obvious reduction in the cumulative number of new infections in each group.
In addition, if the vaccination coverage rate in the 0–17 age group was increased to 40%, 60%, and 80% by June 1, 2021, then through normalization, we obtained the reduced cumulative number of new infections were 21,591, 26,746, and 32,708 per increased 100,000 vaccinated individuals, respectively. Furthermore, increasing the vaccination coverage rate for 0–17 and 18–44 age groups would reduce the cumulative number of new infections even more in NYC (Fig. 3B (a–c)).
Impact of vaccination for two age groups
Reduction of cumulative deaths
If we gradually increased the vaccination coverage rate for two age groups (0–17 and 18–44 age groups, 18–44 and 45–64 age groups, or 65–74 and 75–100 age groups, that is, 0–44 age group, 18–64 age group, or 65–100 age group) to 40% by June 1, 2021, then compared with the current vaccination strategy, the 65–100 age group would have the greatest reduction in cumulative deaths, about 83 fewer deaths as of June 1, 2021 (Figure 4A (a)). However, if the vaccination coverage rate in 0–44 age group, 18–64 age group, or 65–100 age group was increased to 60% by June 1, 2021, then, the 65–100 age group would still have the greatest reduction in cumulative deaths, about 110 fewer deaths as of June 1, 2021 (Figure 4A (b)). In general, the vaccination coverage rate was negative correlation with cumulative deaths.
In addition, similar with vaccination for only one age group, the increased vaccination coverage rate would lead to an obvious reduction in the cumulative number of deaths in two age groups, especially for the people at the age of 65–100 (Fig. 4B (a–c)). Specifically, if starting from March 1, 2021, the vaccination coverage rate in the 65–100 age group was gradually increased up to 40%, 60%, and 80% by June 1, 2021 in NYC, then through normalization, we obtained the reduced cumulative number of deaths were 36, 48, and 62 per increased 100,000 vaccinated individuals, respectively.
Reduction of cumulative new infections
If starting from March 1, 2021, we gradually increased the vaccination coverage rate for 0–44 age group, 18–64 age group, or 65–100 age group to 40% by June 1, 2021, then compared with the current vaccination strategy, the 0–44 age group would have the greatest reduction in cumulative new infections, about 24902 fewer new infections as of June 1, 2021 (Figure 5A (a)). In addition, if we gradually increased the vaccination coverage rate for 0–44 age group, 18–64 age group, or 65–100 age group to 60% by June 1, 2021, then the 0–44 age group would still have the greatest reduction in cumulative new infections, about 32034 fewer new infections as of June 1, 2021 (Figure 5A (b)). In general, the vaccination coverage rate was significantly negative correlation with the cumulative new infections in NYC (Figure 5A).
In addition, the increased vaccination coverage rate would lead to an obvious reduction in the cumulative number of new infections per increased 100,000 vaccinated individuals (Fig. 5B (a–c)). Specifically, if starting from March 1, 2021, the vaccination coverage rate in the 0–44 age group was gradually increased to 40%, 60%, and 80% by June 1, 2021, then through normalization, we obtained the reduced cumulative number of new infections were 17,515, 21,581 and 26,263 per increased 100,000 vaccinated individuals, respectively. Furthermore, we found that increasing the vaccination rate for younger age group would reduce the cumulative number of new infections even more in NYC.
Impact of different vaccine allocation schemes
Based on the results of “Impact of vaccination for one age group” section, we found that if we gradually increased the vaccination coverage rate for only one age group (0–17 age group, 18–44 age group, 45–64 age group, 65–74 age group, or 75–100 age group) to 40%, 60% and 80% by June 1, 2021, then compared with the current vaccination strategy, the 0–17 age group would reduce the cumulative number of new infections mostly and the 75–100 age group would reduce the cumulative number of deaths mostly in NYC as of June 1, 2021. Therefore, 0–17 age group was considered as age group A, 75–100 age group was considered as age group B. Based on the current vaccination coverage rate of five age groups, we reallocated a batch of additional vaccines to these two age groups such that as of June 1, 2021, there would be additional 100,000 vaccinated individuals in the 0–17 age group and the 75–100 age group. We evaluated four vaccine allocation schemes as shown in “Impact of age-specific vaccination strategies” section third scenario, and calculated the reduced cumulative number of deaths and new infections in these two age groups. From Fig. 6A, we found that corresponding to four vaccine allocation schemes, compared with the current vaccination strategy, the reduced cumulative number of deaths were 28, 16, 12 and 21, respectively, and the corresponding reduced cumulative number of new infections were 5392, 5726, 14892 and 40688, respectively (Figure 6B). To compare the vaccine allocation scheme which would reduce the cumulative number of deaths and new infections most simultaneously, we mapped the reduced cumulative number of deaths in the four vaccine allocation schemes into the range of 0 to 1 through normalization, that is, the largest reduced cumulative number of deaths in the first allocation scheme was regarded as 1, and then the reduced cumulative number of deaths in the remaining three vaccine allocation schemes (scheme 2, scheme 3, and scheme 4) were scaled as 0.55, 0.44 and 0.74 respectively proportionally. Similarly, the largest reduced cumulative number of new infections in the fourth allocation scheme was regarded as 1, and then the reduced cumulative number of new infections in the remaining three vaccine allocation schemes (scheme 1, scheme 2, and scheme 3) were scaled as 0.13, 0.14 and 0.37 respectively proportionally. Adding the normalized results for the reduced cumulative number of deaths and new infections in each vaccine allocation scheme, then we obtained the final normalized results of the four vaccine allocation schemes (scheme 1, scheme 2, scheme 3 and scheme 4) were 1.13, 0.69, 0.81 and 1.74 respectively. Therefore, we obtained the fourth vaccine allocation scheme (0–17 age group accounted for 80% and 75–100 age group accounted for 20%) was the most optimal, the reduced cumulative numbers of deaths and new infections were 21 and 40,688 per increased 100,000 vaccinated individuals, respectively, which could ensure the greatest reduction in the cumulative number of deaths and new infections simultaneously in NYC (Figure 7).