COVID-19: Good to Know

A nurse is giving a vaccine to a patient in a classroom.

We still receive many questions about COVID-19 and especially about vaccinations against the virus. Our experts answer the frequently asked questions here and they also explain the importance of vaccination – not only to protect yourself, but also to make a valuable contribution to society.

60 Seconds of Science: Which side effects do I need to expect after a COVID-19 vaccination? (as of August 2021)

You may have heard from some side effects, which others were facing after a COVID-19 vaccination. Some of them are normal and we call them vaccine reactions. Our expert Dr. Konstanze Diefenbach explains the difference between a severe side effect of the vaccination and a vaccine reaction and what you can do against it.  

60 Seconds of Science: When will herd immunity be reached for COVID-19? (as of August 2021)  

One of the most important question about COVD-19 is if and when the coronavirus pandemic will ever really end. We asked our expert Dr. Konstanze Diefenbach to explain what herd immunity means, when it will be reached and what you can do get to support a return to normality.  


FAQ on COVID-19 Vaccines and Virus Variants // Status: October 2021

COVID-19 vaccines have proven to be safe, effective and lifesaving.

Vaccines are Safe. For vaccines authorization or approval to be granted, they need to meet the quality, safety and efficacy criteria defined by international and local regulatory agencies. In terms of efficacy, vaccines need to protect against COVID-19 (e.g. how well the vaccine prevents symptomatic disease).

Note that conditional approval of COVID-19 vaccines is being done on the basis of robust data quality, safety and efficacy. Specifically, the European Medicines Agency defines assessment of efficacy through this process: COVID-19 vaccine developers need to submit specific data on their vaccine. EMA then carries out a thorough assessment of these data to reach a scientific opinion on whether the vaccine is safe, efficacious and of good quality and is therefore suitable to vaccinate people. Efficacy is measured by looking at how well the vaccine works in the study, for example how well the vaccine prevents symptomatic disease.

Vaccines are effective.  After a vaccine is approved or authorized, it continues to be studied to determine how well it works under real-world conditions (vaccine effectiveness). The goal of these assessments is to understand more about the protection a vaccine provides under routine care, beyond the clinical trials. Vaccine effectiveness studies conducted to date indicate that vaccines offer similar protection in real-world conditions as they have in clinical trial settings, reducing the risk of COVID-19, including severe illness, among people who are fully vaccinated.

Current studies such as the “Effectiveness of Covid-19 Vaccines in Ambulatory and Inpatient Care Settings” published last October 7, 2021 by the New  England Journal of Medicine demonstrated that the effectiveness of full messenger RNA (mRNA) vaccination (≥14 days after the second dose) was 89% against laboratory-confirmed SARS-CoV-2 infection leading to hospitalization, 90% against infection leading to an ICU admission, and 91% against infection leading to an emergency department or urgent care clinic visit. 

The effectiveness of full vaccination with respect to a Covid-19–associated hospitalization or emergency department or urgent care clinic visit was similar with the BNT162b2 and mRNA-1273 vaccines and ranged from 81% to 95% among adults 85 years of age or older, persons with chronic medical conditions, and Black or Hispanic adults. The effectiveness of the Ad26.COV2.S vaccine was 68% against laboratory-confirmed SARS-CoV-2 infection leading to hospitalization and 73% against infection leading to an emergency department or urgent care clinic visit. 

Additionally, according to a recent review of data collected from Israel, Sweden the United States of America, and the United Kingdom (including separate data from England and Scotland), all three vaccines (most real-world data relates to the Pfizer/BioNTech, Moderna and Oxford/AstraZeneca vaccines, which were the first to gain emergency authorization in many countries) appeared to reduce people's chances of infection and hospitalization by more than 80% –regardless of their age.

One small study from the US suggested that the Johnson and Johnson vaccine was 76.7% effective in preventing SARS-CoV-2 infection, but there hadn’t been enough hospitalizations, intensive care admissions, or deaths to robustly assess its effectiveness on COVID-19 severity. Meanwhile, a Chilean study of the Sinovac vaccine suggested that it was 65.9% effective at preventing infections, and 87.5% effective against hospitalizations.

What is known currently is that receiving the complete vaccination course results to a high level of protection against the virus. However, it is not established how long immunity or protection against COVID-19 lasts after the vaccination.

Yes, COVID-19 vaccination helps protect you even if you’ve already had COVID-19. Evidence is showing that people get better protection by being fully vaccinated compared with having had COVID-19 and acquire antibodies naturally. 

The reason the COVID-19 vaccines were developed in a shorter time than the previous vaccines is due to investment and technology. This acceleration does not mean compromising any steps of the studies that were related to the safety of the vaccines. 

There are several studies on the vaccine effectiveness against SARS CoV-2 and its variants. While comparisons are made by different groups of scientists in different scenarios and using different variables where some vaccines would show superiority over the other, all the current vaccines publicly available show effective protection against getting infected, suffering from severe illness and death which is the essential trait of an effective vaccine regardless of its type. 

There is a need to prioritize groups at higher risk of COVID-19 for vaccination. When there is a limited supply of the vaccines.

The WHO recommends that protecting individuals and health systems as well as minimizing the impact on economies would be a core goal in the allocation of COVID-19 vaccines across different countries. When vaccine supply is still limited, immunization programs will have to prioritize certain groups over others before progressively expanding distribution to all population groups. 

The precise definition of priority groups is done according to national law. It is based on the most thorough analysis of evidence, including differences across diverse geographical and social settings. WHO suggested that the frontline workers in health and social care settings, the people over the age of 65 and  the people under the age of 65 who have underlying health conditions that put them at a higher risk of death should be prioritized in that particular order. Countries usually follow this recommendation.

Based on available scientific information, it is safe to receive flu vaccines at least 14 days before or after receiving COVID 19 vaccine. Flu vaccination is still of great value in preventing Influenza which is another public health concern. We recommend to inform the attending physician about your vaccination history to receive appropriate advice.

All viruses including SARS-CoV-2, the virus that causes COVID-19, evolve over time. When a virus replicates or makes copies of itself, it sometimes changes a little bit, which is normal for a virus. These changes are called “mutations”. A virus with one or more new mutations is referred to as a “variant” of the original virus. Genetic variants of SARS-CoV-2 have been emerging and circulating around the world throughout the COVID-19 pandemic.

When a virus is widely circulating in a population and causing many infections, the likelihood of the virus mutating increases. The more opportunities a virus has to spread, the more it replicates – and the more opportunities it has to undergo changes. Most viral mutations have little to no impact on the virus’s ability to cause infections and disease. But depending on where the changes are located in the virus’s genetic material, they may affect a virus’s properties, such as transmission (for example, it may spread more or less easily) or severity (for example, it may cause more or less severe disease).

WHO, in collaboration with partners, expert networks, national authorities, institutions and researchers have been monitoring and assessing the evolution of SARS-CoV-2 since January 2020. During late 2020, the emergence of variants that posed an increased risk to global public health prompted the characterization of specific Variants of Concern (VOCs) and Variants of Interest (VOIs), in order to prioritize global monitoring and research, and ultimately to inform the ongoing response to the COVID-19 pandemic. At the present time, experts convened by WHO has recommended using labeled using letters of the Greek Alphabet, such as Alpha, Beta, Gamma, Delta, Kappa and so on, when referring to the SARS-CoV-2 variants.

A VOC is defined as a variant for which there is evidence of an increase in transmissibility, more severe disease (e.g., increased hospitalizations or deaths), significant reduction in neutralization by antibodies generated during previous infection or vaccination, reduced effectiveness of treatments or vaccines, or diagnostic detection failures. As of August 27, 2021, the following variants are considered VOC by the WHO:

B.1.1.7   Alpha   United Kingdom
B.1.351 Beta  South Africa
P.1 Gamma  Brazil
B.1.617.2 Delta India

SARS-CoV-2 isolate is a Variant of Interest (VOI) which has been identified to cause community transmission/multiple COVID-19 cases/clusters, or has been detected in multiple countries; OR is otherwise assessed to be a VOI by WHO in consultation with the WHO SARS-CoV-2 Virus Evolution Working Group.

C.37 Lambda Peru
B.1.621 Mu Colombia

According to WHO COVID-19 Weekly Epidemiological Update published last October 5, 2021, globally, cases of the Alpha variant have been reported in 195 countries, territories or areas while 145 countries have reported cases of the Beta variant; and 99 countries have reported cases of the Gamma variant. The Delta variant has been reported in 192 countries across all six WHO regions as of 5 October. 

The emergence of more transmissible variants when coupled with the relaxation and inappropriate use of public health and social measures (PHSM) and increased social mobility and mixing, and low vaccination coverage in some countries contribute to high incidence, hospitalizations and deaths. There still remain gaps in epidemiological surveillance, testing, and genomic sequencing, and this limits the authorities’ ability to monitor and assess the impact of current and future variants in a timely manner.

The SARS-CoV-2 Delta (B.1.617.2) variant of concern (VOC) was first detected in India in late 2020, where it is thought to have contributed to the extremely high number of cases during the country’s second wave of COVID-19. Since then cases  of COVID-19 due to the Delta variant have been reported in more than 192 countries. 

One country where the Delta variant has taken hold is the UK. Since the first cases were detected in February, it has rapidly overtaken the so-called Alpha (B.1.1.7) variant that was first detected in Kent, England, and which was itself 43 to 90% more transmissible than pre-existing variants of SARS-CoV-2. Delta currently accounts for more than 91% of UK COVID-19 cases, and is around 60% more transmissible than the Alpha variant, according to UK authorities. However, other scientists have calculated it may be 30-100% more transmissible than Alpha. There are studies that show Delta variant approximately double the risk of hospitalization compared with the Alpha variant. People with underlying conditions were at greater risk of being hospitalized, it found.

The COVID-19 vaccines that are currently in development or have been approved elicit a broad immune response involving a range of antibodies and cell response. Several clinical studies show that vaccines offer higher protection against Delta variant after two doses than partial or first dose. Data continues to be collected and analyzed on new variants of the COVID-19 virus.

Vaccines are a critical tool in the battle against COVID-19, and there are scientific studies that support the public health and lifesaving benefits to using the tools we already have. We must not put off getting vaccinated because of our concerns about new variants. In fact, it is strongly medically recommended to proceed with vaccination to have protection against COVID-19 virus even its variants.

Authorities recommend full vaccination of all groups at increased risk of severe COVID-19 as early as possible to reduce the risk of hospitalizations and deaths. In order to achieve maximum protection in the shortest time possible, it is recommended that individuals at highest risk of severe outcomes for COVID-19 receive a second vaccine dose in the shortest possible interval following the administration of the first dose.

Stopping the spread at the source remains the key. Current measures in the community to reduce transmission – including frequent hand washing, wearing a mask, physical distancing, good ventilation and avoiding crowded places or closed settings – continue to work against new variants by reducing the amount of viral transmission and therefore also reducing opportunities for the virus to mutate.

ECDC recommendation is that Non-pharmaceutical interventions (such as physical distancing, hand and respiratory hygiene, use of face masks, etc.) to reduce SARS-CoV-2 transmission are essential elements of the public health response to COVID-19. Therefore, these measures should continue to be in place, complied with, and adjusted to the local epidemiological situation, the vaccination coverage in the general population, and the prevalence of VOC.

Global authorities advise scaling up vaccine manufacturing and rolling out vaccines as quickly and widely as possible to be critical ways of protecting people before they are exposed to the virus and the risk of new variants. According to WHO, ensuring equitable access to COVID-19 vaccines is more critical than ever to address the evolving pandemic. As more people get vaccinated, we expect virus circulation to decrease, which will then lead to fewer mutations.

To date, the evidence for the widespread need for booster doses following a primary vaccination series remains limited and still inconclusive.
WHO, with support of the Strategic Advisory Group of Experts (SAGE) on Immunization and its COVID-19 Vaccines Working Group, continues to review the emerging evidence on the need for and timing of a booster dose for the currently available COVID-19 vaccines which have received Emergency Use Listing (EUL). This statement reflects the current understanding of vaccine performance and supply, as of the time of update.

WHO Definitions: The following definitions and terminology are used by WHO throughout its policy recommendations on COVID-19 vaccination. This note focuses only on booster doses.

  • Booster doses are administered to a vaccinated population that has completed a primary vaccination series (currently one or two doses of COVID-19 vaccine depending on the product) when, with time, the immunity and clinical protection has fallen below a rate deemed sufficient in that population.
    • The objective of a booster dose is to restore vaccine effectiveness from that deemed no longer sufficient.
  • Additional doses of a vaccine may be needed as part of an extended primary series for target populations where the immune response rate following the standard primary series is deemed insufficient. 
    • The objective of an additional dose in the primary series is to optimize or enhance the immune response to establish a sufficient level of effectiveness against disease.
    • Immunocompromised individuals often fail to mount a protective immune response after a standard primary series, but also older adults may respond poorly to a standard primary series.

Rationale for the administration of booster doses
The current primary goal of immunization in the COVID-19 pandemic remains to protect against hospitalization, severe disease and death. Hence, booster doses may only be needed if there is evidence of insufficient protection against these disease outcomes over time. 

The degree of waning of immunity and need for booster doses of vaccine may differ between vaccine products, target populations, circulating SARS CoV-2 virus, in particular variants of concern (VoC), and intensity of exposure. For some vaccines, restricted booster indications have been included into the product label of some jurisdictions. 
In a period of continued global vaccine supply shortage equity considerations at country, regional and global level remain an essential consideration to assure vaccination of high priority groups in every country. Improving coverage of the primary vaccination series should be prioritized over booster vaccination.

Introducing booster doses should be firmly evidence-driven and targeted to the population groups in greatest need. The rationale for implementing booster doses should be guided by evidence on waning vaccine effectiveness, in particular a decline in protection against severe disease in the general population and in high-risk populations, or due to a circulating VoC. To date, the evidence remains limited and still inconclusive on any widespread need for booster doses following a primary vaccination series.