[BostonCard]

https://marlin-prod.literatumonline.com/...326611.pdf

It explains how some individuals came to receive a half-dose for their initial dose:

Two  dosage  groups  were  included  in  COV002:  participants  who  received  a  low  dose  of  the  vaccine  (2·2 × 10¹⁰  viral  particles)  as  their  first  dose  and  were  boosted  with  a  standard  dose  (in  the  LD/SD  group),  and  subse  quent  cohorts  who  were  vaccinated  with  two standard-dose vaccines (SD/SD group). Initial dosing in COV002 was with a batch manufactured at a contract manufacturing    organisation    using    chromatographic    purification. During quality control of this second batch, differences  were  observed  between  the  quantification  methods  (spectrophotometry  and  quantitative  PCR  [qPCR])  prioritised  by  different  manufacturing  sites.  In  consultation with the national regulator (Medicines and Healthcare  products  Regulatory  Agency),  we  selected  a  dose  of  5  ×  10¹⁰  viral  particles  by  spectrophotometer  (2·2 × 10¹⁰  viral  particles  by  qPCR),  in  order  to  be  consistent  with  the  use  of  spectrophotometry  in  the  phase  1  study  (COV001),5  and  to  ensure  the  dose  was  within  a  safe  and  immunogenic  range  according  to  measurements  by  both  methods.  A  lower-than-antici-pated  reactogenicity  profile  was  noted  in  the  trial,  and  unexpected  interference  of  an  excipient  with  the  spec-trophotometry  assay  was  identified.  After  review  and  approval by the regulator, it was concluded that the qPCR (low-dose) reading was more accurate and further doses were adjusted to the standard dose (5 ×  10¹⁰ viral particles) using  a  qPCR  assay.  The  protocol  was  amended  on  June  5,  2020,resulting  in  enrolment  of  two  distinct  groups  with  different  dosing  regimens  with  no  pause  in enrolment (version 6.0; appendix 2 p 330). A suite of assays  has  now  been  developed  for  characterisation  of  concentration  (which  confirmed  the  low  and  standard  dosing),  and  future  batches  are  all  released  with  a  specification  dose  of  3·5–6·5 × 10¹⁰  viral  particles,  and  this was used for the booster doses in the efficacy analysis presented here.

One thing that I had been looking for is how well the vaccine prevents severe disease:

More than 21 days after their first dose, ten participants were  hospitalised  due  to  COVID-19  (defined  as  WHO  clinical  progression  score  ≥4),  two  of  whom  were  assessed  as  having  severe  COVID-19  (WHO  score  ≥6),  including one fatal case. All ten cases were in the control group (table 5).

So, with limited data (only 10 events), it does look like both the standard and low dose vaccines were effective in preventing serious COVID-19.

BC

[BostonCard]

https://marlin-prod.literatumonline.com/...326611.pdf

It explains how some individuals came to receive a half-dose for their initial dose:

Two  dosage  groups  were  included  in  COV002:  participants  who  received  a  low  dose  of  the  vaccine  (2·2 × 10¹⁰  viral  particles)  as  their  first  dose  and  were  boosted  with  a  standard  dose  (in  the  LD/SD  group),  and  subse  quent  cohorts  who  were  vaccinated  with  two standard-dose vaccines (SD/SD group). Initial dosing in COV002 was with a batch manufactured at a contract manufacturing    organisation    using    chromatographic    purification. During quality control of this second batch, differences  were  observed  between  the  quantification  methods  (spectrophotometry  and  quantitative  PCR  [qPCR])  prioritised  by  different  manufacturing  sites.  In  consultation with the national regulator (Medicines and Healthcare  products  Regulatory  Agency),  we  selected  a  dose  of  5  ×  10¹⁰  viral  particles  by  spectrophotometer  (2·2 × 10¹⁰  viral  particles  by  qPCR),  in  order  to  be  consistent  with  the  use  of  spectrophotometry  in  the  phase  1  study  (COV001),5  and  to  ensure  the  dose  was  within  a  safe  and  immunogenic  range  according  to  measurements  by  both  methods.  A  lower-than-antici-pated  reactogenicity  profile  was  noted  in  the  trial,  and  unexpected  interference  of  an  excipient  with  the  spec-trophotometry  assay  was  identified.  After  review  and  approval by the regulator, it was concluded that the qPCR (low-dose) reading was more accurate and further doses were adjusted to the standard dose (5 ×  10¹⁰ viral particles) using  a  qPCR  assay.  The  protocol  was  amended  on  June  5,  2020,resulting  in  enrolment  of  two  distinct  groups  with  different  dosing  regimens  with  no  pause  in enrolment (version 6.0; appendix 2 p 330). A suite of assays  has  now  been  developed  for  characterisation  of  concentration  (which  confirmed  the  low  and  standard  dosing),  and  future  batches  are  all  released  with  a  specification  dose  of  3·5–6·5 × 10¹⁰  viral  particles,  and  this was used for the booster doses in the efficacy analysis presented here.

One thing that I had been looking for is how well the vaccine prevents severe disease:

More than 21 days after their first dose, ten participants were  hospitalised  due  to  COVID-19  (defined  as  WHO  clinical  progression  score  ≥4),  two  of  whom  were  assessed  as  having  severe  COVID-19  (WHO  score  ≥6),  including one fatal case. All ten cases were in the control group (table 5).

So, with limited data (only 10 events), it does look like both the standard and low dose vaccines were effective in preventing serious COVID-19.

BC