Anhui Zhifei Longcom COVID-19 vaccine

Extended version of the vaccine

Anhui Zhifei Longcom COVID-19 vaccine

Authorization

World Health Organization Emergency Use Listing Procedure
Not authorized
Expression of interest accepted [last checked at WHO EUL official website on 9 June 2021].

European Commission (based upon the recommendation of the European Medicines Agency [EMA])
Not authorized.

China's National Medical Products Administration
Authorized [China's National Medical Products Administration, 2021 ].
17 March 2021
Conditional marketing authorization in individuals 18 years of age and older.

Regulatory Authorities of Regional Reference in the Americas

National Administration of Drugs, Foods and Medical Devices (ANMAT, Argentina)
Not authorized.

Brazilian Health Regulatory Agency (ANVISA, Brazil)
Not authorized.

Health Canada
Not authorized.

Public Health Institute (ISP, Chile)
Not authorized.

National Institute of Food and Drug Monitoring (INVIMA, Colombia)
Not authorized.

Center for the State Control of Drug Quality (CECMED, Cuba)
Not authorized.

U.S. Food and Drug Administration (FDA)
Not authorized.

Federal Commission for the Protection against Sanitary Risk (COFEPRIS, Mexico)
Not authorized.

Authorization in other jurisdictions in the Americas
Not authorized.

Authorization in other jurisdictions
Uzbekistan

Manufacturing

Manufacturer
Anhui Zhifei Longcom Biopharmaceutical Co.Ltd.; China. Sponsor of the vaccine clinical trials and main manufacturer [Business Insider, 2021 ].

Other manufacturers
None at this moment.

General characteristics

Anhui Zhifei Longcom COVID-19 vaccine is an adjuvanted protein subunit COVID-19 vaccine. The protein subunit vaccine targets the receptor-binding domain (RBD) for SARS-CoV-2 located at C-terminal domain of S1 subunit in S protein (between R319 to K537) [An Y, 2021 ].

The protein was engineered as a tandem-repeat dimeric RBD to increase immunogenicity. Compared to the traditional monomeric RBD, RBD-dimer enhances the SARS-CoV-2 neutralizing antibodies [Dai L, 2020 ].
RBD is considered an attractive coronavirus vaccine target, because it focuses in the antibody response to block the receptor binding, therefore, poses low potential for antibody-dependent enhancement risk [Dai L, 2020 ].
The construct of RBD-dimer is produced in clinical-grade Chinese hamster ovary (CHO) cell lines and then formulated with aluminum hydroxide as adjuvant, resulting in the final vaccine product [An Y, 2021 ].


Dosage form and ingredients
The pharmaceutical form is a suspension for intramuscular injection that is provided in a monodose vial of 0.5 mL.

The vaccine contains the following ingredients:
Active ingredient:
Recombinant SARS-CoV-2 RBD protein 25 µg
Excipients:
Aluminum hydroxide adjuvant 0.25 mg
Sodium chloride
Disodium phosphate
L-Histidine

Risk considerations

Peptide-based vaccines have theoretical advantages over traditional whole-organism and other platforms [Reche PA, 2014 ]. They allow the immune response to focus on the protective epitopes and to exclude non-relevant epitopes, including those reactogenic or allergenic, at the stage of vaccine design [Reche PA, 2014 ].

Dosification and schedule

Dose-finding studies
The NCV-Ⅰ-healthy phase 1 trial (50 participants) and the NCV-ⅠI-healthy phase 2 trial (900 participants) assessed two different doses (25 µg and 50 µg) in a two-dose or three-dose schedule. The highest SARS-CoV-2 neutralizing response was recorded in the 25 µg/three-dose group [Yang S, 2021 ].

There is no evidence yet about the effects of the coadministration of Anhui Zhifei Longcom COVID-19 vaccine with other vaccines included in routine vaccination programs

Indications and contraindications

Indications
Anhui Zhifei Longcom COVID-19 vaccine is indicated in adult individuals 18 years of age and older [Central Drugs Standard Control Organization of the Government of India, 2021 ].

Contraindications
The vaccine is contraindicated in individuals with a known history of a severe allergic reaction to any component of vaccines.
The second dose of the vaccine should NOT BE GIVEN to those who have experienced anaphylaxis to the first dose of Anhui Zhifei Longcom COVID-19 vaccine.

Precautions
Severe allergic reaction (e.g., anaphylaxis) to a previous dose of any vaccine (not including Anhui Zhifei Longcom COVID-19 vaccine).
In general, persons with an immediate non-anaphylactic allergic reaction to the first dose should not receive additional doses, unless recommended after review by a health professional with specialist expertise.
Vaccination should be postponed in individuals suffering from acute severe febrile illness, or acute infection.
Reactions related to stress or anxiety, such as syncope or hyperventilation may occur in association with vaccination as a psychogenic response to the needle injection. It is important that precautions are in place to avoid injury from fainting.
As with other intramuscular injections, the vaccine should be given with caution in individuals with bleeding disorders or other conditions that increase the risk of bleeding, such as anticoagulant therapy, thrombocytopenia and hemophilia.
The interaction of concomitant administration of Anhui Zhifei Longcom COVID-19 vaccine with other vaccines has not been studied.
The available data on Anhui Zhifei Longcom COVID-19 vaccine on pregnant women are insufficient to assess vaccine efficacy in pregnancy since no clinical trial evaluating vaccines to prevent COVID-19 has included pregnant women. The vaccine should only be given to pregnant women if risks outweigh the benefit.
The available data of the COVID-19 vaccine on lactating females are insufficient to assess whether the vaccine is excreted in human milk or if there is any associated risk.
The available data of the COVID-19 vaccine on children are insufficient to assess vaccine efficacy since no clinical trial evaluating vaccines to prevent COVID-19 has included children.
There should be a minimum interval of 14 days between the administration of this vaccine with any other vaccine in the immunization schedule, until data on co-administration with other vaccines are available.
Vaccination may be offered regardless of a person‘s history of symptomatic or asymptomatic SARS-CoV-2 infection.
Although there are currently no medical contraindications on the vaccinating of a person with COVID-19, it is recommended to defer all vaccinations until complete recovery [PAHO, 2020 ].
Although there are currently no contraindications on the vaccinating of a person who has had contact with a COVID-19 case, it is recommended to defer vaccination until the quarantine has been completed (14 days after the last exposure) [PAHO, 2020 ].

Close observation for at least 30 minutes is recommended following vaccination.

Storage and logistics

Storage
Anhui Zhifei Longcom COVID-19 vaccine is provided as a suspension stored at 5°C/41°F (between 2°C to 8°C [35°F to 46°F]).
Protect the vials from light.
Do not freeze.
Logistic at the time of administration
Inspect the vial before use.
The vial should be discarded if particles or differences are observed in the described appearance of the vaccine.
Shake the vial gently.

Storage after first puncture
After the first puncture of the vial, preferably use immediately.
Record the date and time the vial should be discarded.
To improve traceability, the name and batch number of the administered product should be clearly recorded.
Administration
1.Using aseptic technique, clean the vial stopper with a single-use antiseptic swab.
2. Use a 3 mL reuse prevention syringe (RUP) or a 5 mL RUP syringe, and a 21G or narrower needle.
3. Gently invert the vial to mix, and withdraw the 0.5 mL dose. If the amount of vaccine remaining in the vial cannot provide a full 0.5 mL dose, discard the vial and the remaining volume.
4. Administer the vaccine intramuscularly, preferably into the deltoid muscle. Do not administer the vaccine intravascularly, subcutaneously, or intradermally.

Disposal
Due to the high risk that discarded vials of COVID-19 vaccines may be recovered, it is essential that they are guaranteed to be safely disposed of at the site of use; or study the possibility of applying reverse logistics, if the safe treatment and disposal of vaccine residues cannot be guaranteed, so that they are transferred to the place established for that purpose. Otherwise, consider the possibility that the discarded vaccine vials are shredded, if there is a safe way to do so [WHO, 2021 ].
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Clinical studies - general characteristics

Randomized trials
NCV-Ⅰ-healthy is a phase 1 randomized trial (registered with the number NCT04466085 [Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd., 2020 ]) sponsored by Anhui Zhifei Longcom Biopharmaceutical that is being conducted in China [Yang S, 2021 ]. It was first registered in June 2020 and has enrolled 50 healthy adults aged 18-59 years that received three doses of the vaccine (25 µg or 50 µg) or placebo intramuscularly, 30 days apart in a 2:2:1 ratio. It is expected to run until September 2021. The first report of outcome data published in a scientific journal was released in March 2021.

NCV-Ⅱ-healthy is a phase 2 randomized trial (registered with the number NCT04466085 [Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd., 2020 ]) sponsored by Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd. that is being conducted in China [Yang S, 2021 ]. It was first registered in July 2020 and has enrolled 900 healthy people aged 18 to 59 years that received the vaccine (25 µg or 50 µg) or placebo intramuscularly, 30 days apart, in either a two-dose schedule or a three-dose schedule in a 1:1:1:1:1:1 ratio. It is expected to run until December 2021. The first report of outcome data published in a scientific journal was released in March 2021.

Ongoing randomized trials
LKM-2020-NCV-GJ01 is an ongoing phase 3 randomized trial (registered with the number NCT04646590) sponsored by Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd. that is being conducted in China [Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd., 2020 ]. It was first registered in November 2020 and plans to enroll 29000 healthy adults 18 years and older that will receive 25 µg of the vaccine in a 0, 1 and 2 month immunization schedule. It is expected to run until April 2022.

Methods used to assess efficacy and effectiveness

There are no phase 3 randomized trials that have yet reported outcome data.

Methods used to assess safety

There are no phase 3 randomized trials that have yet reported outcome data.

Efficacy and effectiveness of the vaccine

Efficacy of the vaccine in preclinical studies

The immunogenicity of the vaccine was evaluated in mice and nonhuman primates [An Y, 2021 ].

To study the immunogenicity, groups of BALB/c mice were vaccinated with two doses of 10 µg of the vaccine, 21 days apart. Mice receiving placebo (adjuvant only) were used as negative control. Serum samples from mice were collected at different time points after vaccination to monitor the duration of antibody responses. The geometric mean titer was 256 on day 35, after the second dose, the mean titers remained high until the last sample was taken at 140 days, suggesting that the humoral responses induced by the vaccine would be durable in time [An Y, 2021 ].

Young rhesus macaques were immunized with two doses of 25 µg or 50 µg vaccine intramuscularly, 21 days apart. Macaques that received a placebo were used as controls. The results showed that both doses elicited high levels of serological RBD-binding IgG and SARS-CoV-2 neutralizing antibodies after one or two immunizations [An Y, 2021 ].

Efficacy of the vaccine in clinical trials

Main immunogenicity outcomes

Combined analysis of NCV-Ⅱ-healthy and NCV-Ⅰ-healthyphase 1/2 trials. Phase 1 trial enrolled 50 participants that were assigned to receive three doses of placebo (n=10), the 25 µg vaccine (n=20), or the 50 µg vaccine (n=20). The mean age of participants was 32.6 years. Phase 2 trial enrolled 900 participants that were assigned to receive different schemes of vaccination. One group of participants was assigned to receive two doses of placebo (n=150), 25 µg vaccine (n=150), or 50 µg vaccine (n=150). While, the second group was assigned to receive three doses of placebo (n=150), 25 µg vaccine (n=150), or 50 µg vaccine (n=150). The mean age of participants was 43.5 years [Yang S, 2021 ].

In the phase 1 trial, the main immunogenicity outcome was measured with the serological RBD-binding IgG titres with ELISA test to assess antibody responses. Results showed that seroconversion rates, at day 30 after the second dose, reached 93% (14 of 15 participants) in the 25 µg group and 94% (17 of 18 participants) in the 50 µg group. The SARS-CoV-2-neutralising GMTs were 14% (95% CI 8-24.6) in the 25 µg group and 11.4% (95% CI 6.6-19.8) in the 50 µg group at day 30 after the second dose, and increased to 94.5% (95% CI 49.3-181.3) in the 25 µg group and 117.8% (95% CI 64.6-214.9) in the 50 µg group at day 7 after the third dose [Yang S, 2021 ].

In the two-dose groups in phase 2 of the trial, on day 14 after the third dose, seroconversion rates were 0% (none of 140) in the placebo group, 99% (143 of 144) in the 25 µg group and 97% (139 of 143) in the 50 µg group. The neutralizing GMTs for SARS-CoV-2, 14 days after the second dose were 17.7% (95% CI: 13.6-23) in the 25 µg group and 14% (95% CI : 10.8-18.3) in the 50 µg group. While in the group that received all three doses, the neutralizing GMTs of SARS-CoV-2 14 days later were 102.5% (95% CI: 81.8-128.5) in the group of 25 µg and 69% (95% CI 53-90) in the 50 µg group [Yang S, 2021 ].


Contracting COVID-19

The risk of contracting any COVID-19 infection has not yet been reported, so it was not possible to estimate the effect for this outcome.

Contracting severe COVID-19

The risk of contracting any COVID-19 infection has not yet been reported, so it was not possible to estimate the effect for this outcome.


Efficacy and effectiveness of the vaccine on subgroups

Sex

Randomized trials
There are no phase 3 randomized trials that have yet reported outcome data.

The differential efficacy of the vaccine in sex groups was not reported in the NCV-Ⅰ-healthy phase 1 trial and the NCV-Ⅱ-healthy phase 2 trial [Yang S, 2021 ].

Age

Randomized trials
There are no phase 3 randomized trials that have yet reported outcome data.

The differential efficacy of the vaccine in different age groups was not reported in the NCV-Ⅰ-healthy phase 1 trial and the NCV-Ⅱ-healthy phase 2 trial [Yang S, 2021 ].

Children and adolescents

Randomized trials
There are no phase 3 randomized trials that have yet reported outcome data.

Children and adolescents were excluded from the NCV-Ⅰ-healthy phase 1 trial and the NCV-Ⅱ-healthy phase 2 trial, so no data are available for this subgroup [Yang S, 2021 ].

Pregnancy

Randomized trials
There are no phase 3 randomized trials that have yet reported outcome data.

Pregnant females were excluded from the NCV-Ⅰ-healthy phase 1 trial and the NCV-Ⅱ-healthy phase 2 trial, so no data are available for this subgroup [Yang S, 2021 ].

Breast-feeding

Randomized trials
There are no phase 3 randomized trials that have yet reported outcome data.

Breastfeeding females were excluded from the NCV-Ⅰ-healthy phase 1 trial and the NCV-Ⅱ-healthy phase 2 trial, so no data are available for this subgroup [Yang S, 2021 ].

Immunocompromised persons

Randomized trials
There are no phase 3 randomized trials that have yet reported outcome data.

Immunocompromised participants were excluded from the NCV-Ⅰ-healthy phase 1 trial and the NCV-Ⅱ-healthy phase 2 trial, so no data are available for this subgroup [Yang S, 2021 ].

Other data from vaccine efficacy and effectiveness

Duration of protection

Randomized trials
The exact duration of protection afforded by the vaccine is unknown as it is still being determined by ongoing clinical trials.

Comparative studies
None available.

Non-comparative studies
None available.

Limitations of vaccine effectiveness

Individuals may not be fully protected until 14 days after their second dose. As with all vaccines, vaccination with Anhui Zhifei Longcom COVID-19 vaccine may not protect all vaccine recipients.

SARS-CoV-2 variants

Randomized trials
None available.

Other studies
Huang et al evaluated the reduction in neutralization against variant beta (also known as B.1.351, first documented in South Africa) by sera from 12 recipients of Anhui Zhifei Longcom COVID-19 vaccine The study concluded that sera from the vaccine recipients did neutralize this variant [Huang B, 2021 ].

Cao et al evaluated the reduction in neutralization against variant beta by sera from 20 recipients of Anhui Zhifei Longcom COVID-19 vaccine. The study concluded that sera from the vaccine recipients did neutralize this variant [Cao Y, 2021 ].

Safety of the vaccine

Safety of the vaccine in preclinical studies

Safety outcomes were not assessed in the animal studies available [An Y, 2021 ].

Safety of the vaccine in clinical trials

Any adverse event

The combined analysis of NCV-Ⅱ-healthy and NCV-Ⅰ-healthy, the most common solicited systemic adverse events were cough, fever, and headache. Two (10%) grade 3 adverse events were reported in the 50 µg group. In the phase 2 trial, the overall frequency of adverse events after 30 days of vaccination, among participants receiving two doses, was 37 (25%) of 150 participants in the placebo group, 43 (29%) of 150 participants in the 25 µg group, and 50 (33%) of 150 participants in the 50 µg group. Participants receiving three doses, 47 (31%) of 150 in the placebo group, 72 (48%) of 150 in the 25 µg group, and 65 (43%) of 150 in the 50 µg group reported at least one adverse event. The most common solicited local adverse events in participants on the two-dose and three-dose schedules were injection-site pain, swelling, induration, redness, and itch. The most common solicited systemic adverse events in participants on the two-dose and three-dose schedules were fever, cough, headaches, and fatigue [Yang S, 2021 ].

Serious adverse events

There are no phase 3 randomized trials that have yet reported outcome data.

In the phase 1/2 trial combined analysis of NCV-Ⅱ-healthy and NCV-Ⅰ-healthy, serious adverse events were not observed [Yang S, 2021 ].


Non-serious adverse events

There are no phase 3 randomized trials that have yet reported outcome data.

In the phase 1/2 trial combined analysis of NCV-Ⅱ-healthy and NCV-Ⅰ-healthy, non-serious adverse events were not observed [Yang S, 2021 ].

Safety of the vaccine in subgroups

Sex

Randomized trials
There are no phase 3 randomized trials that have yet reported outcome data.

The differential safety of the vaccine in sex groups was not reported in the NCV-Ⅰ-healthy phase 1 trial and the NCV-Ⅱ-healthy phase 2 trial [Yang S, 2021 ].

Age

Randomized trials
There are no phase 3 randomized trials that have yet reported outcome data.

The differential safety of the vaccine across age groups was not reported in the NCV-Ⅰ-healthy phase 1 trial and the NCV-Ⅱ-healthy phase 2 trial [Yang S, 2021 ].

Children and adolescents

There are no phase 3 randomized trials that have yet reported outcome data.

Children and adolescents were excluded from the NCV-Ⅰ-healthy phase 1 trial and the NCV-Ⅱ-healthy phase 2 trial, so no data are available for this subgroup [Yang S, 2021 ].

Pregnancy

Randomized trials
There are no phase 3 randomized trials that have yet reported outcome data.

Pregnant females were excluded from the NCV-Ⅰ-healthy phase 1 trial and the NCV-Ⅱ-healthy phase 2 trial, so no data are available for this subgroup [Yang S, 2021 ].

Breast-feeding

Randomized trials
There are no phase 3 randomized trials that have yet reported outcome data.

Breastfeeding females were excluded from the NCV-Ⅰ-healthy phase 1 trial and the NCV-Ⅱ-healthy phase 2 trial, so no data are available for this subgroup [Yang S, 2021 ].

Immunocompromised persons

Randomized trials
There are no phase 3 randomized trials that have yet reported outcome data.

Immunocompromised participants were excluded from the NCV-Ⅰ-healthy phase 1 trial and the NCV-Ⅱ-healthy phase 2 trial, so no data are available for this subgroup [Yang S, 2021 ].

Safety of the vaccine post-authorization

Post-authorization studies

Comparative studies
None available.

Non-comparative studies
None available.

Case reports and case series
None available.

Spontaneous report data

Disclaimer: Reporting suspected adverse reactions after authorization of the medicinal product is important because it allows continuous monitoring of the benefit/risk balance of the vaccines. However, they do not indicate a causal association between the vaccine and the observed effects. Furthermore, this information should not be used to estimate the frequency of adverse events in people receiving the vaccine or to make comparisons between different vaccines. The information emerging about possible adverse effects needs to be carefully evaluated in order to first establish if the adverse effect might have been caused by the vaccine.

None available.

Monitoring

WHO recommends the following research and post-authorization monitoring activities:
− monitoring of serious adverse events.
− vaccine effectiveness over time and whether protection can be prolonged by booster doses.
− studies to investigate whether this vaccine reduces SARS-CoV-2 transmission and viral shedding.
− assessment and reporting of vaccination failures and virus sequence information.
− prospective studies on the safety of Anhui Zhifei Longcom COVID-19 vaccine in pregnant and lactating females.
− randomized controlled trials on efficacy and safety of vaccination in children below the age of 18 years.
− safety data on vaccination in immunocompromised persons, including persons living with HIV and persons with autoimmune disease.
− immunogenicity and safety studies of co-administration with other vaccines, including influenza and pneumococcal vaccines, to adults and older persons.
− safety, immunogenicity, and impact of a delayed second dose, as currently implemented by certain countries.
− stability of the vaccine under alternative cold-chain distribution and storage conditions.
− effectiveness of the proposed strategies for the prevention and management of anaphylactic reactions.
− interchangeability studies within and across COVID-19 vaccine platforms.

Vaccination logistics
− immunogenicity and safety studies of co-administration with other vaccines, including influenza and pneumococcal vaccines, to adults and older persons.
− safety, immunogenicity, and impact of a delayed second dose, as currently implemented by certain countries.
− stability of the vaccine under alternative cold-chain distribution and storage conditions.
− effectiveness of the proposed strategies for the prevention and management of anaphylactic reactions.
− interchangeability studies within and across COVID-19 vaccine platforms.

References

[China's National Medical Products Administration, 2021] China's National Medical Products Administration. China approves new type of vaccine for emergency use against COVID-19. Press release - China Daily - 2021-03-17. 2021; China's National Medical Products Administration. China approves new type of vaccine for emergency use against COVID-19. Press release - China Daily - 2021-03-17. 2021;
[Business Insider, 2021] Business Insider. Another Chinese Covid-19 vaccine enters late-stage human trials with a plan to produce 300 million doses annually. News. 2021; Business Insider. Another Chinese Covid-19 vaccine enters late-stage human trials with a plan to produce 300 million doses annually. News. 2021;
[An Y, 2021] An Y, Li S, Jin X et al. A tandem-repeat dimeric RBD protein-based COVID-19 vaccine ZF2001 protects mice and nonhuman primates. bioRxiv. 2021; An Y, Li S, Jin X et al. A tandem-repeat dimeric RBD protein-based COVID-19 vaccine ZF2001 protects mice and nonhuman primates. bioRxiv. 2021;
[Dai L, 2020] Dai L, Zheng T, Xu K et al. A Universal Design of Betacoronavirus Vaccines against COVID-19, MERS, and SARS. Cell. 2020;182(3). Dai L, Zheng T, Xu K et al. A Universal Design of Betacoronavirus Vaccines against COVID-19, MERS, and SARS. Cell. 2020;182(3).
[Reche PA, 2014] Reche PA, Fernandez-Caldas E, Flower DR, Fridkis-Hareli M, Hoshino Y. Peptide-based immunotherapeutics and vaccines. Journal of immunology research. 2014;2014:256784. Reche PA, Fernandez-Caldas E, Flower DR, Fridkis-Hareli M, Hoshino Y. Peptide-based immunotherapeutics and vaccines. Journal of immunology research. 2014;2014:256784.
[Yang S, 2021] Yang S, Li Y, Dai L et al. Safety and immunogenicity of a recombinant tandem-repeat dimeric RBD-based protein subunit vaccine (ZF2001) against COVID-19 in adults: two randomised, double-blind, placebo-controlled, phase 1 and 2 trials. The Lancet. Infectious diseases. 2021;21(8):1107-1119. Yang S, Li Y, Dai L et al. Safety and immunogenicity of a recombinant tandem-repeat dimeric RBD-based protein subunit vaccine (ZF2001) against COVID-19 in adults: two randomised, double-blind, placebo-controlled, phase 1 and 2 trials. The Lancet. Infectious diseases. 2021;21(8):1107-1119.
[Central Drugs Standard Control Organization of the Government of India, 2021] Central Drugs Standard Control Organization of the Government of India. SmPC & PI of Whole Virion Inactivated Corona Virus Vaccine of M/s Bharat Biotech approved for restricted use in emergency situation in Clinical Trial Mode. SUMMARY OF PRODUCT CHARACTERISTICS. 2021; Central Drugs Standard Control Organization of the Government of India. SmPC & PI of Whole Virion Inactivated Corona Virus Vaccine of M/s Bharat Biotech approved for restricted use in emergency situation in Clinical Trial Mode. SUMMARY OF PRODUCT CHARACTERISTICS. 2021;
[PAHO, 2020] PAHO. The Immunization Program in the Context of the COVID-19 Pandemic, 26 March 2020. PAHO/FPL/IM/COVID-19/20-0005. 2020; PAHO. The Immunization Program in the Context of the COVID-19 Pandemic, 26 March 2020. PAHO/FPL/IM/COVID-19/20-0005. 2020;
[WHO, 2021] WHO. COVID-19 vaccination: supply and logistics guidance: interim guidance, 12 February 2021. WHO/2019-nCoV/vaccine_deployment/logistics/2021.1. 2021; WHO. COVID-19 vaccination: supply and logistics guidance: interim guidance, 12 February 2021. WHO/2019-nCoV/vaccine_deployment/logistics/2021.1. 2021;
[Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd., 2020] Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd.. Phase I Clinical Study of Recombinant Novel Coronavirus Vaccine (CHO Cells). clinicaltrials.gov. 2020; Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd.. Phase I Clinical Study of Recombinant Novel Coronavirus Vaccine (CHO Cells). clinicaltrials.gov. 2020;
[Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd., 2020] Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd.. Clinical Study of Recombinant Novel Coronavirus Vaccine. clinicaltrials.gov. 2020; Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd.. Clinical Study of Recombinant Novel Coronavirus Vaccine. clinicaltrials.gov. 2020;
[Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd., 2020] Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd.. A Phase III Clinical Trial to Determine the Safety and Efficacy of ZF2001 for Prevention of COVID-19. clinicaltrials.gov. 2020; Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd.. A Phase III Clinical Trial to Determine the Safety and Efficacy of ZF2001 for Prevention of COVID-19. clinicaltrials.gov. 2020;
[Huang B, 2021] Huang B, Dai L, Wang H et al. Serum sample neutralisation of BBIBP-CorV and ZF2001 vaccines to SARS-CoV-2 501Y.V2. The Lancet. Microbe. 2021; Huang B, Dai L, Wang H et al. Serum sample neutralisation of BBIBP-CorV and ZF2001 vaccines to SARS-CoV-2 501Y.V2. The Lancet. Microbe. 2021;
[Cao Y, 2021] Cao Y, Yisimayi A, Bai Y et al. Humoral immune response to circulating SARS-CoV-2 variants elicited by inactivated and RBD-subunit vaccines. Cell research. 2021; Cao Y, Yisimayi A, Bai Y et al. Humoral immune response to circulating SARS-CoV-2 variants elicited by inactivated and RBD-subunit vaccines. Cell research. 2021;
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