Everything you need to know about COVID-19 vaccines

Essential information on the efficacy of the COVID-19 vaccines backed by the UK government and their effect on disease transmission and new variants.

Open access article

The Royal Pharmaceutical Society has made this article free to access in order to help healthcare professionals stay informed about an issue of national importance.

To learn more about coronavirus, please visit: https://www.rpharms.com/resources/pharmacy-guides/wuhan-novel-coronavirus

Vaccines have been the success story of the COVID-19 pandemic, with three already approved for use in the UK, and promising late-stage trial results for a further two vaccines backed by the UK government.

This feature illustrates how each type of vaccine works, and brings together key data for pharmacists on the vaccines currently available, as well as those in the pipeline. It will be updated regularly to include the latest information.

Although data on vaccine efficacy are included, direct comparisons between vaccines are not possible owing to the trials using different endpoints and taking place at different times — when there were differing case rates and circulating variants.

Click on the following links to take you to the vaccines you want to learn more about:

mRNA vaccines: Pfizer/BioNTech; Moderna

Adenoviral vector vaccines: University of Oxford/AstraZeneca; Janssen

Protein-based vaccines: Novavax; GSK/Sanofi

Inactivated whole virus vaccines: Valneva

mRNA vaccines

mRNA vaccines are made using a new technology, which — in the case of COVID-19 — uses a nanoparticle to deliver the genetic instructions for human cells to make the SARS-CoV-2 spike protein, priming the immune system to attack the SARS-CoV-2 virus if it later infects the body (see Figure).

Pfizer/BioNTech (BNT162b2)

Is it approved in the UK?

Yes, it was authorised for temporary supply on 2 December 2020.

How many doses have been ordered?

40 million.

What are the storage requirements?

  • Store between -80°C and -60°C. Shelf life is 6 months.
  • After thawing, undiluted vaccine can be stored for up to 5 days at 2–8°C, and up to 2 hours at temperatures up to 25°C.
  • Once diluted, store at between 2–25˚C and use within 6 hours.

What are the latest data on effectiveness?

Phase II/III study results, published on 31 December 2020, suggest that a two-dose regimen of BNT162b2 confers 94.6% protection against symptomatic COVID-19, at least 7 days following the second dose. One case of severe COVID-19 occurred in the vaccine group compared with 9 in the placebo group.

Since then, several ‘real-world’ studies have been published. Data from an observational study of 7,000 healthcare workers in Israel suggests that vaccine efficacy against symptomatic COVID-19 infection is 85% from 15–28 days after the first dose. And further data from Israel’s mass vaccination programme estimates vaccine efficacy at days 14 through 20 after the first dose, and at 7 or more days after the second dose as follows: for documented infection, 46% (95% confidence interval [CI] 40–51) and 92% (95% CI 88–95); for symptomatic COVID-19, 57% (95% CI 50–63) and 94% (95% CI 87–98); for hospitalisation, 74% (95% CI 56–86) and 87% (95% CI 55–100); and for severe disease, 62% (95% CI 39–80) and 92% (95% CI 75–100), respectively. Estimated effectiveness in preventing death from COVID-19 is 72% (95% CI 19–100) for days 14 through 20 after the first dose.

Early data from Public Health England’s (PHE’s) prospective SIREN study of healthcare workers, published as a pre-print on 22 February 2021, suggests vaccine efficacy of 72% (95% CI 58–86) against asymptomatic and symptomatic infection 21 days after the first dose and 86% (95% CI 76–97) 7 days after the second dose.

And observational data from a US study of healthcare personnel, first responders, and other essential and frontline workers, published by the Centers for Disease Control and Prevention (CDC) on 29 March 2021, suggest vaccine efficacy for mRNA vaccines (Pfizer/BioNTech and Moderna) is 80% (95% CI 59%–90%) against asymptomatic and symptomatic infection at least 14 days after the first dose and 90% (95% CI 68%–97%) at least 14 days after the second dose.

This high efficacy is sustained for at least six months, according to Pfizer/BioNTech, which announced an updated topline analysis of their phase III trial on 1 April 2021. The analysis suggests that the vaccine efficacy is 91.3% (95% CI 89.0–93.2) against COVID-19 up to six months after the second dose. The analysis also suggests vaccine efficacy is 100% (95% CI 88.0–100.0) and 95.3%  (95% CI 71.0–99.9) against severe disease, as defined by the CDC and the US Food and Drug Administration, respectively.

Pfizer/BioNTech have also announced topline results from a trial in adolescents (31 March 2021), which found that the vaccine efficacy was 100% in over 2,000 participants aged 12 to 15 years old, with 18 cases in the placebo group and none in the vaccine group.

Is it effective against new variants?

Yes, but effectiveness may be reduced against some variants and more data are needed.

UK variant (B.1.1.7): A small laboratory study using vaccine sera suggests roughly equivalent neutralisation of  this variant. And data from the UK vaccination programme, published as a pre-print on 1 March 2021, and the PHE SIREN study, suggest vaccine efficacy is still high against B.1.1.7.

South African variant (B.1.351): A small laboratory study using vaccine sera suggests a 10.3-fold reduction in antibodies that neutralise this variant. However, analysis of 800 participants in Pfizer/BioNTech’s phase III trial, announced by the companies on 1 April 2021, shows nine cases of COVID-19 in the placebo group, six of which were due to B.1.351, and none in the vaccine group, suggesting vaccine efficacy of 100% (95% CI 53.5–100.0).

Brazilian variant (P1): A small laboratory study using vaccine sera suggests roughly equivalent neutralisation of this variant, although two other laboratory studies, published as preprints, suggest antibody titres were reduced by 2.6-fold and 14-fold. The impact is yet to be confirmed in clinical trials.  

Does it work in older people?

Yes.

Data from the UK vaccination programme suggest vaccine efficacy in those aged ≥70 years reached 58% (95% CI 49–65) from 28 days after vaccination, before plateauing.

Individuals who receive one dose have an additional 42% (95% CI 32–51) lower risk of emergency hospitalisation, and an additional 54% (95% CI 41–64) lower risk of death, making a single dose of the vaccine 80% effective at preventing hospitalisation.

In a study published as a pre-print on 1 March 2021, vaccine efficacy in those aged ≥80 years was 59% (95% CI 46–68) from 28–34 days after the first dose, then plateaued, before rising to 85% (95% CI 79–89) from 14 days after the second dose.

Data from the mass vaccination programme in Israel also confirms that vaccine efficacy is similar in those aged >70 years, and in younger age groups, after the second dose.

Does it reduce transmission?

Yes, but we need more data to know the extent of the reduction.

Data from Israel, published in a pre-print on 8 February 2021, suggest that infections occurring 12 days or longer following vaccination have significantly reduced viral loads, potentially affecting viral shedding and contagiousness as well as severity of the disease.

On 18 February 2021, an observational study of 7,000 vaccinated healthcare workers in Israel, published in The Lancet, found that all COVID-19 infections (symptomatic and asymptomatic) were reduced by 75%, suggesting an impact on transmission. And data announced by the Israel Ministry of Health and Pfizer/BioNTech on 15 March 2021 suggest that vaccine efficacy is 94% against asymptomatic infections 2 weeks after the second dose.

Results from the SIREN study, conducted among healthcare workers in England and published in a pre-print in The Lancet on 22 February 2021, suggest vaccine efficacy against all infections is 72% after one dose and 86% after two doses.

A UK study of healthcare workers at Cambridge University Hospitals NHS Foundation Trust, published as a pre-print on 24 February 2021, found a four-fold decrease in the risk of asymptomatic infection among healthcare workers ≥12 days post-vaccination, compared with unvaccinated healthcare workers.

And a study led by Public Health Scotland and the University of Glasgow, published as a pre-print on 12 March 2021, examining infections in nearly 150,000 vaccinated and unvaccinated healthcare workers and 200,000 of their household members, provides the first direct evidence of a reduction in transmission. There was a 30% reduction in documented cases of infection in household members of vaccinated compared with unvaccinated healthcare workers (hazard ratio [HR] 0.70, 95% CI 0.63–0.78), which the researchers estimate translates to a 60% reduction in transmission since household members could be infected by other routes. A 54% reduction in documented cases in household members was observed ≥14 days after the second dose (HR 0.46, 95% CI 0.30—0.70). Participants received either the Pfizer/BioNTech vaccine or the Oxford/AstraZeneca vaccine.

An observational study in the US, published on 29 March 2021, also confirmed that both asymptomatic and symptomatic infections are reduced by 90% at least 14 days after the second dose.

Are there any safety concerns?

The safety profile reflects that seen in clinical trials (injection-site reactions and generalised ‘flu-like’ symptoms).

Full product information can be viewed here.

Moderna (mRNA-1273)

Is it approved in the UK?

Yes, it was authorised for temporary supply on 3 January 2021, and given a conditional marketing authorisation on 1 April 2021.

How many doses have been ordered?

17 million.

What are the storage requirements?

  • Store between -25º and -15ºC. Shelf life is 7 months.
  • Once thawed, unopened vials can be stored at 2–8 °C for up to 30 days or at 8– 25°C for 12 hours.
  • After opening, store at 2–25˚C and use within 6 hours.

What are the latest data on effectiveness?

Vaccine efficacy was 94.1% (95% CI 89.3–96.8) against symptomatic infection 14 days after the second dose in clinical trials. No cases of severe COVID-19 occurred in the vaccine group compared with 30 in the placebo group.

Observational data from a US study of healthcare personnel, first responders, and other essential and frontline workers, published by the Centers for Disease Control and Prevention on 29 March 2021, suggest vaccine efficacy for mRNA vaccines (Pfizer/BioNTech and Moderna) is 80% against asymptomatic and symptomatic infection at least 14 days after the first dose and 90% at least 14 days after the second dose.

Does it work against new variants?

Yes, but effectiveness may be reduced against some variants and more data are needed.

UK variant (B.1.1.7): A small laboratory study suggest no significant difference, but this is yet to be demonstrated in clinical trials.

South African variant (B.1.351): A small laboratory study suggest a 6.5-fold reduction in antibodies that neutralise this variant, but this is yet to be demonstrated in clinical trials.

Brazilian variant (P1): A small laboratory study suggests antibody titres are reduced by 2.6-fold. The impact is yet to be confirmed in clinical trials.

Does it work in older people?

Yes, in clinical trials.

In clinical trials, vaccine efficacy was 86.4% (95% CI 61.4–95.2) against symptomatic infection 14 days after the second dose in those aged >65 years.

Does it reduce transmission?

More than likely, but we need more data.

Data from swabs taken during clinical trials to check for asymptomatic infections, submitted to the US Food and Drug Administration by Moderna, suggest transmission could be reduced by two-thirds after one dose, but the number of asymptomatic infections was small and the data have not yet been peer reviewed.

An observational study in the US, published on 29 March 2021, also confirmed that both asymptomatic and symptomatic infections are reduced by 90% at least 14 days after the second dose.

Are there any safety concerns?

The safety profile reflects that seen in clinical trials (injection-site reactions and generalised ‘flu-like’ symptoms).

Full product information can be viewed here.

Adenoviral vector vaccines

Adenoviral vector vaccines are made using a relatively new technology, which uses a common cold virus to deliver the genetic instructions for human cells to make the SARS-CoV-2 spike protein, priming the immune system to attack the SARS-CoV-2 virus if it later infects the body (see Figure).

Oxford/AstraZeneca (ChAdOx1 nCoV-19 [AZD1222])

Is it approved in the UK?

Yes, it was authorised for temporary supply on 30 December 2020.

How many doses have been ordered?

100 million.

What are the storage requirements?

  • Store at 2–8ºC. Shelf life is 6 months.
  • After opening, store at 2–25˚C and use within 6 hours.

What are the latest data on effectiveness?

Data released as a pre-print in The Lancet on 2 February 2021 suggest vaccine efficacy against symptomatic infection is 76% (95% CI 59–86) after a single dose in individuals aged 18–55 years, increasing to 82.4% (95% CI 62.7–91.7) after a second dose administered 12+ weeks later. There were no hospitalisations or deaths in the vaccine group.

AstraZeneca announced results of a study in 32,449 participants in the US, Peru and Chile on 25 March 2021, which suggests vaccine efficacy is 76% (95% CI 68–82) against symptomatic disease, and 100% against severe or critical disease and hospitalisation when two doses are given four weeks apart.

Does it work against new variants?

Yes and no.

UK variant (B.1.1.7): Real-world data from the UK vaccination programme, published as a pre-print on 1 March 2021, suggest there is high vaccine efficacy against the UK variant. And study data published in The Lancet on 30 March 2021 show that, although neutralising antibody titres generated by the vaccine were nine-fold lower for the UK variant, vaccine efficacy against symptomatic cases was similar for B.1.1.7 and non-B1.1.7 lineages (70.4% [95% CI 43·6–84·5] and 80.5% [95% CI 67·9–89·4], respectively).

South African variant (B.1.351): A small laboratory study using vaccine sera suggests a 12.4-fold reduction in antibodies that neutralise this variant. A study published in The New England Journal of Medicine on 16 March 2021 suggests that a two-dose regimen has an efficacy of only 10.4% (95% CI −76.8 to 54.8) against mild to moderate COVID-19 infection in almost 1,500 HIV-negative young adults. Efficacy against severe COVID-19 infection from this variant was not assessed.

Brazilian variant (P1): A small laboratory study using vaccine sera suggests antibody titres were reduced by 2.9-fold against this variant.

Does it work in older people?

Yes.

Data from the UK vaccination programme, published on 17 March 2021, suggest vaccine efficacy in those aged ≥70 years is 56% (95% CI 43–65) from 28–34 days after receiving the vaccine, and increases to 58% (95% CI 38–72) from day 35 onwards. Individuals who received one dose had an additional 35% (95% CI 4–56) lower risk of emergency hospitalisation, making one dose of vaccine approximately 80% effective at preventing hospitalisation. There was insufficient follow-up to assess the vaccine’s effect on deaths.

Results of the US study confirm this, with a vaccine efficacy of 85% (95% CI 58–95) in those aged >65 years after two doses, four weeks apart.

Does it reduce transmission?

Yes, but we need more data to know the extent of the reduction.

Data released as a pre-print in The Lancet on 2 February 2021, which looked at the number of symptomatic and asymptomatic cases, suggest it could reduce transmission by 67%. However, a study published in The Lancet on 30 March 2021, found that vaccine efficacy against asymptomatic cases of the B.1.1.7 variant was only 28·9% (95% CI −77·1–71·4) compared with 69·7% (95% CI 33·0–86·3) for non-B.1.1.7 infections, although fewer cases were available for analysis, so confidence intervals were wide and overlapping. 

And a study led by Public Health Scotland and the University of Glasgow, published as a pre-print on 12 March 2021 and examining infections in nearly 150,000 vaccinated and unvaccinated healthcare workers and 200,000 of their household members, provides the first direct evidence of a reduction in transmission. There was a 30% reduction in documented cases of infection in household members of vaccinated compared with unvaccinated healthcare workers (HR 0.70, 95% CI 0.63–0.78), which the researchers estimate translates to a 60% reduction in transmission since household members could be infected by other routes. A 54% reduction in documented cases in household members was observed ≥14 days after the second dose (HR 0.46, 95% CI 0.30—0.70). Participants received either the Pfizer/BioNTech vaccine or the Oxford/AstraZeneca vaccine.

Are there any safety concerns?

The safety profile generally reflects that seen in clinical trials (injection-site reactions and generalised ‘flu-like’ symptoms).

However, on 7 April 2021, a rigorous safety review by the Medicines and Healthcare products Regulatory Agency (MHRA) of 79 UK reports of blood clotting cases alongside low levels of platelets following use of the Oxford/AstraZeneca vaccine for 20.2 million doses, concluded that evidence of a link between the vaccine and this extremely rare adverse event is getting stronger, although more work is still needed.

The Joint Committee on Vaccination and Immunisation (JCVI) advised that any remaining unvaccinated adults in phase 1 of the programme who are aged 18 to 29 years old and do not have an underlying health condition that puts them at higher risk from serious covid-19 should be offered an alternative vaccine, if available. The JCVI explained that, given the very low numbers of events reported overall, there is currently a high level of uncertainty in estimates of the incidence of this adverse event by age group. However, the available data suggest a slightly higher incidence reported in younger adults, who are also at lowest risk of serious COVID-19. The benefits of prompt vaccination with the Oxford/AstraZeneca vaccine far outweigh the risk of adverse events for individuals 30 years and over and those who have underlying health conditions which put them at higher risk of severe COVID-19, it added.

The MHRA advised careful consideration before administering the vaccine to people at higher risk of blood clots because of a medical condition, and that a second dose should not be given to those who experienced this adverse event after the first dose. Vaccine recipients should also be advised to look out for symptoms four days or more after vaccination, including new onset of severe or persistent headache, blurred vision, confusion or seizures, shortness of breath, chest pain, leg swelling or persistent abdominal pain, and unusual skin bruising or pinpoint round spots beyond the injection site.

Full product information can be viewed here.

Janssen (Ad26.COV2.S)

Is it approved in the UK?

No.

How many doses have been ordered?

30 million.

What are the storage requirements?

Store at -20ºC for 2 years or 2–8ºC for 3 months.

What are the latest data on effectiveness?

Data submitted to the United States Food and Drug Administration suggest vaccine efficacy is 66.1% (95% CI 55.01; 74.80) overall against moderate to severe disease (72.0% [95% CI 58.2–81.7] in the United States) 28 days after vaccination. It was 85.4% (95% CI 54.15–96.90) effective in preventing severe to critical disease. Vaccine efficacy against COVID-19 requiring medical intervention (defined as hospitalisation, intensive care unit admission, mechanical ventilation, extracorporeal membrane oxygenation) was 100.0% (95% CI 31.11–100.0) at least 28 days after vaccination.

Does it work against new variants?

Yes, although more data are needed.

UK variant (B.1.1.7): Phase III study did not include UK participants.

South African variant (B.1.351): Data submitted to the United States Food and Drug Administration suggest 64.0% (95% CI 41.2–78.7) against moderate and severe disease.

Brazilian variant: Data submitted to the United States Food and Drug Administration 68.1% (95% CI 48.8, 80.7) against moderate and severe disease.

Does it work in older adults?

Yes, although more data are needed.

Data submitted to the United States Food and Drug Administration suggest a vaccine efficacy of 67.9% (95% CI 38.2–82.8) 28 days after vaccination in participants aged ≥60 years, although participants aged ≥60 years without comorbidities had a higher vaccine efficacy estimate than participants aged ≥60 years with comorbidities. Further follow-up data are needed to help understand these potential differences.

Does it reduce transmission?

Probably, but we need more data.

Preliminary data submitted to the United States Food and Drug Administration show the vaccine reduced the risk of infection in a subgroup of 2,650 participants by 65.5% (95% CI 39.91–81.08), suggesting an impact on transmission, but this finding needs to be further investigated with additional data.

Are there any safety concerns?

The safety profile in clinical trials includes injection-site reactions and generalised ‘flu-like’ symptoms.

Full product information can be viewed here.

Protein-based vaccines

Protein-based vaccines are made using an older technology, which delivers SARS-CoV-2 spike proteins directly into the body, along with an adjuvant, priming the immune system to attack the SARS-CoV-2 virus if it later infects the body (see Figure).

Novavax (NVX-CoV2373)

Is it approved in the UK?

No.

How many doses have been ordered/pre-ordered?

60 million.

What are the storage requirements?

Store at 2–8 ºC.

What are the latest data on effectiveness?

Data from a final analysis of a phase III UK trial involving more than 15,000 participants, announced by Novavax on 15 March 2021, suggest vaccine efficacy is 89.7% (95% CI 80.2–94.6) against symptomatic infection at least seven days after the second dose. No severe cases occurred in the vaccine group compared with five in the placebo group.

Does it work against new variants?

Yes, but vaccine effectiveness may be reduced against some variants and more data are needed.

UK variant (B.1.1.7): Data from Novovax suggests 86.3% (95% CI 71.3–93.5) against symptomatic infection.

South African variant (B.1.351): Data from Novovax suggests 48.6% (95% CI 28.4–63.1) against symptomatic infection, 55.4% (95% CI 35.9–68.9) in HIV-negative participants.

Brazilian variant (P1): No evidence yet.

Does it work in older people?

Yes, although more data are needed.

Just over a quarter (27%) of trial participants were aged >65 years; there was one case of COVID-19 in the vaccine group compared with nine in the placebo group.

Does it reduce transmission?

We don’t know yet.

Animal studies suggest transmission can be prevented entirely but this has not yet been confirmed in humans.

Are there any safety concerns?

Analyses of the UK and South Africa trials showed that the vaccine is well-tolerated, with low levels of severe, serious and medically attended adverse events at day 35, balanced between vaccine and placebo group.

Full product information is not yet available.

GSK/Sanofi

Is it approved in the UK?

No.

How many doses have been ordered/pre-ordered?

60 million.

What are the storage requirements?

Store at 2–8ºC.

What are the latest data on effectiveness?

Clinical trials have been delayed after weaker responses were observed in older people likely owing to an insufficient concentration of the antigen in the vaccine. The vaccine will be reformulated and trialled again.

Does it work against new variants?

We don’t know yet.

UK variant (B.1.1.7): No evidence yet.

South African variant (B.1.351): No evidence yet.

Brazilian variant: No evidence yet.

Does it work in older adults?

Not in early trials.

Phase I/II trial results announced by GSK/Sanofi showed insufficient neutralising antibody titres in adults over the age of 50 years.

Does it reduce transmission?

We don’t know yet.

Data not yet available.

Are there any safety concerns?

Data not yet available.

Full product information is not yet available.

Inactivated whole virus vaccines

Inactivated whole virus vaccines are made using an old technology, which delivers an inactivated version of the SARS-CoV-2 virus directly into the body, along with an adjuvant, priming the immune system to attack the SARS-CoV-2 virus if it later infects the body (see Figure).

Valneva (VLA2001)

Is it approved in the UK?

No.

How many doses have been ordered/pre-ordered?

100 million.

What are the storage requirements?

Store at 2–8ºC.

What are the latest data on effectiveness?

Phase I/II trial results in 153 healthy adults aged 18 to 55 years old, announced by Valneva on 6 April 2021, suggest the vaccine is immunogenic, with more than 90% of all study participants developing significant levels of antibodies to the SARS-CoV-2 virus spike protein across three dose groups tested. In the high dose group, after two doses, antibody titres were at or above levels for a panel of convalescent sera. 

Does it work against new variants?

We don’t know yet.

UK variant (B.1.1.7): No evidence yet.

South African variant (B.1.351): No evidence yet.

Brazilian variant (P1): No evidence yet.

Does it work in older adults?

We don’t know yet.

Data not yet available.

Does it reduce transmission?

We don’t know yet.

Data not yet available.

Are there any safety concerns?

Phase I/II trial results, announced by Valneva on 6 April 2021, suggest the vaccine is well tolerated with no safety concerns identified.

Full product information is not yet available.

Panel: Priority groups for vaccination 

Phase 1:

  1. Residents in a care home for older adults and their carers
  2. All those aged 80 years and over, and frontline health and social care workers
  3. All those aged 75 years and over
  4. All those aged 70 years and over, and clinically extremely vulnerable individuals
  5. All those aged 65 years and over
  6. All those aged 16–64 years with underlying health conditions that put them at higher risk of serious disease and mortality, and adult household contacts of adults with severe immunosuppression
  7. All those aged 60 years and over
  8. All those aged 55 years and over
  9. All those aged 50 years and over

Phase 2:

  1. All those aged 40–49 years
  2. All those aged 30–39 years
  3. All those aged 18–29 years

The Joint Committee on Vaccination and Immunisation strongly advises the following groups to take up a vaccine as soon as it is offered:

  • Men
  • People from black, Asian and minority ethnic communities
  • People with a body mass index over 30
  • People living in socio-economically deprived areas

Latest:

  • The Oxford/AstraZeneca entry was updated to include a new announcement from the Joint Committee on Vaccination and Immunisation following a Medicines and Healthcare products Regulatory Agency review of reports of blood clots and low platelets after receiving the vaccine.
  • The Pfizer/BioNTech entry was updated to include topline results on vaccine efficacy in adolescents announced by the companies on 31 March 2021.
  • The Pfizer/BioNTech entry was updated to include topline results on vaccine efficacy in adults up to six months after the second dose, and on vaccine efficacy against the South African variant, announced on 1 April 2021.
  • The Moderna entry was updated to indicate that it received a conditional marketing authorisation on 1 April 2021.
  • The Valneva entry was updated to include phase I/II trial results, announced on 6 April 2021.

Illustrations: Alisdair Macdonald

Editorial advisers for the illustrations: Stephen Griffin, associate professor and chair, Virus Division, Microbiology Society, University of Leeds; Charles Bangham, chair in immunology and co-director of the Institute of Infection at Imperial College London.

Last updated
Citation
The Pharmaceutical Journal, April 2021;Online:DOI:10.1211/PJ.2021.1.71237