Table 3 Direct effects of vaccines and duration of immunity following vaccination as reported by studies fulfilling inclusion criteria

1

Shrotri et al. (2021) [17]

BNT162b2 increased S-antibody levels to a median of 7506 U/mL (IQR 4925–11 950) at 21–41 days, and ChAdOx1 increased S-antibody levels to a median of 1201 U/mL (IQR 609–1865) at 0–20 days

The authors reported a significant trend of decline in S-antibody levels with time for both AstraZeneca (ChAdOx1) and Pfizer (BNT162b2) vaccines. Specifically, about five-fold and two-fold reductions from peak antibody levels were observed in ChAdOx1 and BNT162b2 respectively, 70 days or more post-second dose vaccination. While S-antibody levels reduced from a median of 7506 U/mL (IQR 4925–11 950) at 21–41 days, to 3320 U/mL (1566–4433) at 70 or more days in the BNT162b2 group, S-antibody levels reduced from a median of 1201 U/mL (IQR 609–1865) at 0–20 days to 190 U/mL (67–644) at 70 or more days in the ChAdOx1 group

2

Shu et al. (2021) [20]

V-01 provoked substantial immune responses in the two-dose group, achieving encouragingly high titres of neutralising antibody and anti-RBD immunoglobulin, which peaked at day 35 (161.9 [95% confidence interval [CI]: 133.3–196.7]

Not applicable

3

Tsatsakis et al. (2021) [15]

The vaccine induced high level of anti-SARS-CoV-2 antibody titres (ranging from 0.26 to 14.16, with a mean value of 4.23 ± 2.76) following complete vaccination

The time of sampling after the second vaccine dose appeared to negatively correlate with antibody titres starting from the third week post-vaccination

4

Levin et al. (2021) [21]

The vaccine induced SARS-CoV-2 antibody with the highest titres (peak) observed during days 4 through 30, after the receipt of the second dose

Six months after receipt of the second dose, neutralising antibody titres were substantially lower among men than among women (ratio of means, 0.64; 95% confidence interval [CI], 0.55 to 0.75), lower among persons 65 years of age or older than among those 18 to less than 45 years of age (ratio of means, 0.58; 95% CI, 0.48 to 0.70), and lower among participants with immunosuppression than among those without immunosuppression (ratio of means, 0.30; 95% CI, 0.20 to 0.46)

5

Favresse et al. (2021) [22]

The vaccine induced antibody response reaching maximal level between days 28 and 42 (2204 versus 1,863; P = 0.20)

A significant antibody decline was observed at 3 months compared to the peak response

6

Taylor et al. (2021) [23]

The vaccines gave a high % neutralising antibodies two weeks after the second dose. Also, the Johnson and Johnson vaccine gave positive neutralising antibody levels after several weeks

At peak concentration, an approximate threefold difference in titer was observed between individuals and all samples exhibited a sharp initial decline in neutralizing antibodies that began to tail off approximately 30 days after the second dose

7

Terpos et al. (2021) [24]

The vaccines induced a median NAb inhibition titre of 62.8% (for patients with myeloma) and 90% for healthy subjects (controls)

Not applicable

8

Flaxman et al. (2021) [25]

ChAdOx1 nCoV-19 induced high antibody titres especially those with longer interval between first and second vaccinations

Not applicable

9

Collier et al. (2021) [26]

The vaccine induced significantly higher geometric mean neutralisation titre (GMT) and increased IgG

Not applicable

10

Ella et al. (2021) [27]

BBV152 induced high neutralising antibody and showed better reactogenicity and safety outcomes, enhancing humoral and cell-mediated immune responses

Not applicable

11

Glockner et al. (2021) [28]

All vaccines induced higher levels of neutralising antibodies in healthy subjects when compared to subjects after a mild infection

At 4–5 weeks of double vaccination, S-IgG levels were 1755 BAU/mL (95% CI: 1219–2527) but at final follow-up (13 weeks), S-IgG levels decreased to 806.6 (95% CI: 598–1087)

12

Goldberg et al. (2021) [29]

The rate of confirmed SARS-CoV-2 infections was significantly lower among the fully vaccinated indicating increased immunity

Findings indicate that immunity against the delta variant of SARS-CoV-2 waned across all age groups a few months post full vaccination

13

Guerrera et al. (2021) [30]

The vaccine induced the development of a sustained anti-viral memory T cell response which includes both the CD4 + and the CD8 + lymphocyte subsets

The vaccine induced antibodies decrease over time, though the antibodies were maintained at high levels for at least 6 months post full vaccination

14

Chu et al. (2021) [31]

The vaccine resulted in significant immune responses to SARS-CoV-2. It induced bAb and nAb by 28 days postvaccination one. Following second vaccination, binding antibodies and nAb increased substantially by 14 days

Not applicable

15

Israel et al. (2021) [32]

Not applicable

The authors reported a gradual increase in the risk of breakthrough infections among participants who received their second vaccine dose after at least 146 days (Please note: Findings from this study should be taken cautiously as it was a preprint at the time of screening).

16

Khoury et al. (2021) [33]

The vaccine induced antibody titres which reached a climate after one month of the second dose of the vaccine

Antibody titre drops rapidly one month after the second dose of the vaccine

17

Frater et al. (2021) [34]

The vaccine induced anti-spike IgG responses by ELISA which peaked at day 42 and were sustained until day 56

Not applicable

18

Nanduri et al. (2021) [35]

Effectiveness estimates showed that the vaccines protect against SARS-CoV-2 infection among nursing home residents

Not applicable

19

Richmond et al. (2021) [36]

SCB-2019 induced immune responses against SARS-CoV-2. It increased the IgG antibodies, ACE2-competitive binding antibodies and neutralising antibodies against SARS-CoV-2

Authors reported that titres waned from their peak at days 36–50, but SCB-2019 IgG antibodies, ACE2-competitive binding antibodies and neutralising antibodies against wild type SARS-CoV-2 persisted at 25–35% of their observed peak levels at Day 184

20

Racine-Brzostek et al. (2021) [37]

The vaccine generated antibody levels similar, if not superior, to the antibody levels induced by natural SARS-CoV-2 infection

The authors reported a decrease in total and neutralising antibodies among participants that were never diagnosed with SARS-CoV-2 four weeks post-second dose vaccination

21

Naaber et al. (2021) [38]

The vaccine induced robust antibody response to Spike protein after the second dose

The antibody levels declined at 12 weeks and 6 months post-vaccination, indicating a waning of the immune response over time

22

Tartof et al. (2021) [39]

The vaccine effectiveness against SARS-CoV-2 infections was 73% (95% CI 72–74) and against COVID-19-related hospital admissions was 90% (89–92)

Vaccine effectiveness against infections declined from 88% (86–89) during the first month after full vaccination to 47% (43–51) after 5 months

23

Tober-Lau et al. (2021) [40]

Not applicable

Significant decline in markers of immunity at the 6-month follow-up, particularly for older participants

24

Achiron et al. (2021) [41]

Not applicable

Anti-S1 IgG levels determined across 1 to 8 months after full vaccination, waned with an estimated half-life of 45 days

25

Aldridge et al. (2021) [42]

Three weeks after the second dose the vaccines induced substantially higher anti-S levels (BNT162b2 mean anti-S levels were 9039 (95%CI: 7946–10,905) U/ml and ChadOx1 were 1025 (95%CI: 917–1146) U/ml)

Waning for both vaccines began three weeks after the second dose. At 20 weeks after the second dose of vaccine, the mean anti-S levels were 1521 (95%CI: 1432–1616) U/ml for BNT162b2 and 342 (95%CI: 322–365) U/ml for ChAdOx1. Further evidence showed that rates of waning were higher in BNT162b2 (- 8.27e-03 [ln (anti-S U/ml)/day], t1⁄2 = 68.81 days) than ChAdOx1 (-10.1e-03 [ln (anti-S U/ml)/day], t1⁄2 = 84.5 days; p < 0.001). No difference in rates of waning was observed by age and sex for both BNT162b2 and ChAdOx1. Also, there was no evidence of a difference in rates of waning by clinical risk groups for both BNT162b2 and ChAdOx1 cohorts (Please note: Findings from this study should be taken cautiously as it was a preprint at the time of screening)

26

Angel-Korman et al. (2021) [43]

The vaccine induced a positive anti-S antibody titre level but was significantly lower in haemodialysis patients than the non-dialysis-dependent

ultivariate analysis demonstrated a gradual antibody waning in MHD patients, with anti-S titres decreasing by 1.36% (95% CI 0.74–1.38%) and neutralising antibodies by 2.37% (1.29–3.63%) per day, as well as loss of neutralising antibodies with time

27

Chemaitelly et al. (2021) [44]

Estimated BNT162b2 effectiveness against any SARS-CoV-2 infection was 77.5% (95% CI, 76.4 to 78.6) in the first month after the second dose. The peak effectiveness against symptomatic infection was 81.5% (95% CI, 79.9 to 83.0), whereas that against asymptomatic infection was 73.1% (95% CI, 70.3 to 75.5)

Estimated BNT162b2 effectiveness against any SARS-CoV-2 infection was negligible for the first 2 weeks after the first dose, increased to 36.8% (95% confidence interval [CI], 33.2 to 40.2) in the third week after the first dose, and reached its peak at 77.5% (95% CI, 76.4 to 78.6) in the first month after the second dose. However, effectiveness declined gradually, starting from the first month after the second dose. The decline accelerated after the fourth month, and effectiveness reached a low level of approximately 20% in months 5 through 7 after the second dose