Yes. You can still get COVID-19 after vaccination but your chance of becoming infected is greatly reduced by up to 95% after the Pfizer/BioTNech or Moderna vaccines. You are very unlikely to get severe COVID-19 after vaccination. It has not been established that you cannot transmit the virus after vaccination, but it is highly likely that you would be less infectious than someone who hadn’t been vaccinated. This remains to be fully proven.

The currently available vaccination regimen includes two shots. After the first vaccination it takes at least one to three weeks, depending on the age (young people react faster than older ones), to get an efficient protection, based on antibody to the virus titers. This protection is much more rapidly achieved (after a few days) after the second vaccine shot.  In this context it is possible to be infected by SARS-CoV-2 if one is in contact with the virus before vaccination has been fullyachieved and thus to spread the virus. However, preliminary evidence suggests that the likelihood to develop severe COVIDe19 would be reduced.

A recent observational study conducted in England showed the effectiveness of Pfizer vaccine against SARS‑CoV-2 infection by preventing viral transmission. Importantly, this study demonstrates that a complete vaccination with two doses is required to effectively stop transmission. Further studies will be required with other COVID-19 vaccines.

For safety, it is required to keep maintaining strict precautions: wearing masks, respecting physical distancing, and hand washing.

Yes – you can get COVID-19 again, but it is rare.

Natural immunity acquired after COVID-19 infection will last for several months and at least eight months.  Also, there is mounting evidence for a persistent cellular immune protection after such infection. Consistent with this, the number of well documented cases of reinfection has remained very low; yet this may happen. As explained in section 7 this points to the importance of getting vaccination if COVID-19 has happened several months ago. Re-infection with a variant, which is different from the original strain, appears to be occurring more commonly, as recently described in Brazil.

We do not know yet for how long vaccination will be protective again COVID-19.  This information will only be obtained when the results of the ongoing prospective studies will be available. Also, it is very likely that the duration of protection will differ from one vaccine to the other.

Yes, if you had COVID-19 several months ago. Only one shot of vaccine should be sufficient.

It is now clear that the natural immunity acquired after COVID-19 infection will last for several months and at least eight months. However, the level of acquired immunity could be different depending on the individual’s immune system and disease severity. Therefore, it is recommended to get vaccinated for previously infected people with the virus.  Vaccination stimulates a “memory” effect and induces good antibody response as well as the T cell response. This can provide a robust and lasting-immunity.

Two studies showed that the antibody response to the first mRNA vaccine dose in individuals with pre-existing immunity is equal to, or even exceeds, the titers found in naïve individuals after the second dose. Although this needs to be verified, one dose of mRNA vaccine might be sufficient for previously infected people.

If one was treated for COVID-19 symptoms with monoclonal antibodies or convalescent plasma, it is recommended to wait 90 days before getting a COVID-19 vaccine, since reinfection is uncommon in the 90 days after initial infection.

Presently ,there is no rationale to use one over another vaccine and the studies are ongoing to evaluate their respective efficacy. Similarly, safety and efficacy of a serial vaccination with two different types of vaccines have not been evaluated. Such studies are ongoing.

The vaccination campaign has extended worldwide. Specifically, more than 74 Million people have been fully vaccinated in the U.S. Only a very limited number of individuals have shown severe reactions, all of them quickly resolving (most of such persons had significant previous allergic preexisting conditions).

Also, although the evaluation of the vaccines against COVID-19 by the regulatory agencies (FDA, EMEA, UK) has been extremely rapid, it is important to emphasize that there have been no “short cuts” in the development of the SARS-CoV-2/COVID-19 vaccine.  In fact, the overall procedure has been exactly the same as compared with other vaccine evaluations.  In particular, the number of individuals included in the studies compares well with previous evaluation procedures. Also, it is important to note that the companies had transferred their preliminary data to the regulatory agencies in advance and thus the evaluations have been performed on a stringent basis.

A few people have experienced rare types of blood clots after receiving the Oxford-AstraZeneca vaccine, particularly, in Europe, where the AstraZeneca vaccine is widely used. The European Medicines Agency (EMA) has concluded that the Oxford–AstraZeneca COVID-19 vaccine should carry a warning that blood clots, accompanied by low levels of blood platelets, are very rare side effects of the vaccine. Vaccinated people and health-care providers should be aware of blood-clot symptoms, such as shortness of breath, chest pain, leg swelling and persistent abdominal pain, to ensure prompt treatment. However, EMA along with the World Health Organization (WHO) and the Medicines and Healthcare products Regulatory Agency (UK) have stated that the benefits of vaccine still greatly outweighed the risks.

Because of its safety concern, Germany, the Netherlands, the Philippines, Portugal and Spain have recommended vaccination of this vaccine only to people over 60. Canada and France have limited it to those over 55; Australia, over 50; Belgium, over 56. Regulators in France and Germany have recommended that people under 55 who have had one dose get a different vaccine for their second shot. Britain would begin offering alternative shots to people under 30.

On Tuesday, April 13, the US Food and Drug Administration and the Centers for Disease Control Federal health agencies called for an immediate pause in the use of the Johnson & Johnson vaccine after six recipients in the US developed a rare disorder involving blood clots within about two weeks of vaccination. The agencies are currently evaluating its safety.

There is no formal contra-indication to vaccinating pregnant women.  COVID-19 in pregnant women can lead to severe consequences for the mother and the fetus. Thus, regulatory agencies recommend to make the decision based on the risk of exposure to the virus. A recent surveillance study showed the safety of mRNA Covid-19 vaccines (Pfizer and Moderna) in pregnant persons. However, a long-term effect of vaccines on pregnancy needs to be continuously evaluated.

GVN Perspective: Pregnancy and COVID-19 Vaccines – March 5, 2021

This is still being debated and recommendations vary from one country to the other.

Specifically, Moderna and Pfizer (mRNA based vaccine) recommend their standard protocols, 4 weeks apart and 3 weeks apart, respectively. Scientists for the Pfizer vaccine suggested to have the second dose of immunization within 6 weeks after the first immunization (a grace period). US CDC recommends following the standard protocol for each vaccine but waiting up to 42 days between doses can be tolerated.

As for the AstraZeneca vaccine, the clinical trials have shown that vaccine efficacy was 82.4% in the case of a 12-week interval between the two doses as compared with 54.9% for a less than 6-week interval. This supports the UK’s strategy for vaccinating quickly as many as people possible with a single dose to facilitate limited supply. However, more validation studies will be necessary.

Mutations refer to the change in the genomic information (component of DNA or RNA) which leads to synthetize the various components of a virus. Viruses are constantly changing through mutations of their genome.  Most of these mutations will remain silent because they do not provide any advantage to the virus for its dissemination; yet some mutations provide an advantage to the virus and thus are adapted for a better fitness. Indeed, these genetic variations lead to the emergence of variants, that may have different characteristics (virus’ ability to spread, to cause disease or to escape the body’s immune response).

GVN Perspective: Update on SARS-CoV-2 Variants – February 5, 2021

GVN Perspective: Emergence and Global Spread of SARS-CoV-2 Variants – January 26, 2021

Mutations arise as a natural by-product of viral replication. Similar to other RNA viruses, SARS-CoV-2 makes mistakes when it copies its RNA genome. These mutations occur over time and SARS-CoV-2 keeps mutating (evolving) to adapt to the host environment.  Some of these mutations have been described to emerge in people who are immunosuppressed and therefore mount a sub-optimal response to the virus or people who have received antibodies from another person, as part of a treatment called convalescent serum.

GVN Perspective: Why Do Genes and Mutations Matter in SARS-CoV-2? – May 27, 2020

The variants are spreading the same way as the original virus. The variants spread by person-to-person transmission routes. These include direct transmission (cough, sneeze, droplet inhalation transmission) and contact transmission (contact with oral, nasal and eye mucous membranes and to the latter by a contaminated surface).

GVN Perspective: How Long Is a SARS-CoV-2 Infected Person Contagious? – October 23, 2020

Epidemiology data have indicated that the three variants can spread faster than previously known SARS-CoV-2. In particular, the UK variant has shown 30-50% of enhanced transmissibility. Currently, there is no firm evidence that the UK variant may cause more severe disease. These details have not been demonstrated yet for the other variants, and this is being carefully monitored.

GVN Perspective: Should the Global Community Be Concerned About the South African Variant? – February 23, 2021

GVN Perspective: Update on SARS-CoV-2 Variants – February 5, 2021

It is very likely that prior COVID-19 infection protects against the “UK” variant (B.1.1.7) However, recent studies have shown reinfection of previously recovered individuals from COVID-19 with certain variants. Particularly, variants emerged from South Africa and Brazil are known to be immune escape mutants by evading antibodies from previous infections, thus causing  and thus causing reinfection of recovered individuals from COVID-19.

Read more:

Brazil covid-19 variant (P.1)
New Scientist

GVN Perspective: Should the Global Community Be Concerned About the South African Variant? – February 23, 2021

Most countries recommend isolation of people with COVID-19 for 10 days. This is because infectious virus is rarely detected after 8 days. There is no evidence that infectious virus persists for longer with the variants.

Yet, some patients with severe COVID-19 have shown prolonged duration of virus shedding, up to 20 days after symptom onset. Virus shedding does not mean that you are infectious as prolonged shedding is usually associated with very low levels of virus.

Currently, duration of contagiousness for patients infected by the variants has not been clearly tested. However, it is very likely that, similar to previous SARS-CoV-2, individuals will no longer have contagious variant after 8 days.

GVN Perspective: How Long Is a SARS-CoV-2 Infected Person Contagious? – October 23, 2020

Monoclonal antibodies to the viral protein have been shown to efficiently block infection of the human cells by the virus. Recent clinical studies have demonstrated their immediate efficacy to treat early stages of the viral infection.  In fact, they have even suggested that using such antibodies might allow prevention of COVID-19 in at risk individuals.  However, the cost and the IV administration route do presently limit their use.

Regarding their efficacy against variants, it is important to understand that in contrast with vaccines, such monoclonal antibodies are by definition targeting a single component of the viral envelope.  Thus, any mutation at this site would abolish the effect of such monoclonal antibodies.  This has recently led to the use of a combination of several monoclonal antibodies targeting different components of the viral envelope (such as the casirivimab and imdevimab antibody cocktail).  Recent evidence would suggest the efficacy of such an approach against the variants of the UK and South Africa.

No. Current COVID-19 tests cannot detect if a variant is present or not, although some adjusted PCR-based assays have been proposed. This can be done by genomic sequencing analysis. Thus, genetic surveillance will be key to monitor the circulation of these variants.

GVN Perspective: Update on SARS-CoV-2 Variants – February 5, 2021