Dataset from A Phase 1/2 Study of Delayed Heterologous SARS-CoV-2 Vaccine Dosing (Boost) After Receipt of EUA Vaccines

A phase 1/2, open-label clinical trial in individuals, 18 years of age and older, who are in
good health, have no known history of Coronavirus Disease 2019 (COVID-19) or Severe Acute
Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection, and meet all other eligibility
criteria. This clinical trial is designed to assess the safety, reactogenicity and
immunogenicity of a delayed (>/=12 weeks) vaccine boost on a range of Emergency Use
Authorization (EUA)-dosed COVID-19 vaccines (mRNA-1273, and mRNA-1273.211 manufactured by
ModernaTX, Inc.; BNT162b2 manufactured by Pfizer/BioNTech; or Ad26.COV2.S manufactured by
Janssen Pharmaceuticals/Johnson & Johnson). This is an adaptive design and may add arms (and
increase sample size) as vaccines are awarded EUA and/or variant lineage spike vaccines are
manufactured or become available. Enrollment will occur at up to twelve domestic clinical
research sites.

This study includes two cohorts. Cohort 1 will include approximately 880 individuals (50
subjects/group; Groups 1E-11E) greater than 18 years of age and older, stratified into two
age strata (18-55 years and >/=56 years) who previously received COVID-19 vaccine at
Emergency Use Authorization dosing (EUA) (two vaccinations of mRNA-1273 at the 100 mcg dose,
two vaccinations of BNT162b2 at the 30 mcg dose, or one vaccination of Ad26.COV2.S at the
5x10^10 vp dose). Groups 15E-17E will enroll 60 subjects, split (approximately evenly)
between age strata as able. Those subjects will be offered enrollment into this study >/=12
weeks after they received the last dose of their EUA vaccine. Subjects will receive a single
open-label intramuscular (IM) injection of the designated delayed booster vaccine and will be
followed through 12 months after vaccination: 1) Group 1E - previously EUA-dosed vaccination
with Janssen - Ad26.COV.2.S at 5x10^10 vp followed by a 100-mcg dose of mRNA-1273, Group 4E -
previously EUA-dosed vaccination with Janssen - Ad26.COV.2.S at 5x10^10 vp followed by a
5x10^10 vp dose of Ad26.COV2.S, Group 7E - previously EUA-dosed vaccination with Janssen -
Ad26.COV.2.S 5x10^10 vp followed by a 30-mcg dose of BNT162b2, Group 10E - previously
EUA-dosed vaccination with Janssen - Ad26.COV2-S 5x10^10 vp followed by a 100-mcg dose of
mRNA-1273.211; Group 12E - previously EUA-dosed vaccination with Janssen - Ad26.COV2-S
5x10^10 vp followed by a 50-mcg dose of mRNA-1273; Group 15E - previously EUA-dosed
vaccination with Janssen (two doses for Group 15E) - Ad26.COV2.S at 5x1010 vp followed by a
dose of NVX-CoV2373 (5 mcg Prototype SARS-CoV-2 rS vaccine with 50 mcg Matrix-M); 2) Group 2E
- previously EUA-dosed vaccination with Moderna - mRNA-1273 at 100 mcg for two doses followed
by a 100-mcg dose of mRNA-1273, Group 5E - previously EUA-dosed vaccination with Moderna -
mRNA-1273 at 100 mcg for two doses followed by a 5x10^10 vp dose of Ad26.COV2.S, Group 8E -
previously EUA-dosed vaccination with Moderna - mRNA-1273 at 100 mcg for two doses followed
by a 30-mcg dose of BNT162b2, Group 13E - previously EUA-dosed vaccination with Moderna -
mRNA-1273 at 100 mcg for two doses followed by a 50-mcg dose of mRNA-1273; Group 16E -
previously EUA-dosed vaccination with Moderna - mRNA-1273 at 100 mcg for two doses followed
by a dose of NVX-CoV2373 (5 mcg Prototype SARS-CoV2 rS vaccine with 50 mcg Matrix-M); 3)
Group 3E - previously EUA-dosed vaccination with Pfizer/BioNTech - BNT162b2 at 30 mcg for two
doses followed by a 100-mcg dose of mRNA-1273. Group 6E - previously EUA-dosed vaccination
with Pfizer/BioNTech - BNT162b2 at 30 mcg for two doses followed by a 5x10^10 vp dose of
Ad26.COV2.S, Group 9E - previously EUA-dosed vaccination with Pfizer/BioNTech - BNT162b2 at
30 mcg for two doses followed by a 30-mcg dose of BNT162b2, Group 11E - previously EUA-dosed
vaccination with Pfizer/BioNTech - BNT162b2 at 30 mcg for two doses followed by a 100-mcg
dose of mRNA-1273.211. Group 14E - previously EUA-dosed vaccination with Pfizer/BioNTech -
BNT162b2 at 30 mcg for two doses followed by a 50-mcg dose of mRNA-1273, Group 17E -
previously EUA-dosed vaccination with Pfizer/BioNTech - BNT162b2 at 30 mcg for two doses
followed by a dose of NVX-CoV2373 (5 mcg Prototype SARS-CoV2 rS vaccine with 50 mcg
Matrix-M).

A telephone visit will occur one week after each primary EUA vaccination and one week after
the booster dose. In person follow-up visits will occur on 14 days following completion of
EUA vaccinations and on days 14, and 28 days after the booster dose, as well as 3, 6, and 12
months post the booster vaccination. Additional pools of subjects can be included if needed
as additional COVID-19 vaccines are awarded EUA.

The primary objectives of this study are 1) to evaluate the safety and reactogenicity of
delayed heterologous or homologous vaccine doses after EUA dosed vaccines, and 2) to evaluate
the breadth of the humoral immune responses of heterologous and homologous delayed boost
regimens following EUA dosing.