Covid-19 Can Vaccinated person spread the virus?

Dr Umer Farooq
India is in the middle of a second wave of the Covid-19 outbreak. Active cases in the country have been on the rise over the last week with the daily new cases crossing 50,000 regularly. The last time it happened in October 2020, when India was facing its first wave. “After having successfully brought down the number of new Covid-19 cases from mid-September to February, India is now witnessing a rapid rise in cases,” health secretary Rajesh Bhushan said in a letter to the chief secretaries of all the State governments and Union territories on March 30. “The current rise in cases is of concern and has the potential of overwhelming health care systems, unless checked right now.”
A total of 93 thousand new cases of Covid-19 were reported in India in the last 24 hours. In J & K a total of 501 new cases of Covid-19 were reported.
The second wave comes at a time when India has decided to make all its citizens aged above 45 eligible for vaccinations. So far, vaccines were only provided to those on the frontlines before it was extended to those above 60 years and those above the age of 45, but with co-morbidities, were also allowed to vaccinate themselves. Now from April 1, 2021 every citizen above 45 years of age in India is eligible to get vaccinated for Covid-19. So far, some 61 million doses of vaccines have been administered, according to the government, of which 8.4 million people have completed both the first and second dose.
As we continue the vaccination process, an important question that may arise is “Can a vaccinated person get Covid-19 infection and also spread the virus”.
While getting vaccinated gives people considerable assurance against falling ill with Covid-19, but that does not mean a vaccinated person cannot fall ill from Covid-19. No vaccine provides 100% safety or surety that a person will be immune to a certain disease after immunization. The present vaccines have an efficacy of about 79% which means they can protect 79% of new cases from happening compared to non-vaccinated but there is still some chance that the vaccine may fail to protect a vaccinated person.
Moreover after taking a vaccine dose it may take 15 to 20 days for immunity to develop, so until the immunity develops a person may be vulnerable to Covid-19.
Further the Covid-19 vaccine we use in our country needs two doses for providing maximum possible protection, because the efficacy of these vaccines after the first dose is only around 50%. So a person still has a high chance of contracting the virus after the first dose.
Getting a vaccine does not always mean immunity. In other words a vaccinated person may fail to develop immunity even after vaccination is done. There may be various factors involved like, wrong technique, bad vaccine or simply failure of vaccination due to the innate efficacy of vaccines as earlier explained.
A recent news report from Telangana said that about 15 people who had taken both doses of the vaccine had contracted Covid-19 and their symptoms ranged from mild to moderate. The doctors there said that the vaccine may have provided only partial protection and had only reduced the effect of the disease but not fully prevented infection and also the vaccine efficacy may have played a role. This event clearly shows that vaccination does not mean full protection from Covid-19.
Also if an immunized person gets silently infected with Covid-19, they might pass it on, potentially sickening people who aren’t immune because they themselves won’t fall sick but they may still pass the virus to others and become silent carriers. Those who are infected but never develop symptoms are responsible for 24% of transmission, one study estimated. The more Covid-19 circulates, the more opportunity the virus has to mutate in ways that enhance its ability to spread, sicken and kill people, and evade the immunity provided by existing vaccines or a past infection. Already, variants of the virus have emerged that appear to be more dangerous. According to some reports, this 2nd wave of Covid-19 may be due to newer strains of the virus infecting people. These newer strains like UK Strain and Africa Strain of this virus have been detected in many newly positive persons. That may further increase the challenge of controlling the virus and also is a challenge to vaccine developers to make their vaccines effective against these new strains.
Using vaccination to achieve so-called herd immunity, which means an entire community is protected from the disease when most of the people but not everyone has been immunized, requires vaccines that prevent transmission which the present vaccines may not be able to achieve.
Various studies all over the world are being conducted to study the effect of vaccines in preventing infection and transmission. To explore that question, researchers typically give one group of volunteers the experimental vaccine and another group of equal size a placebo. After the total number of volunteers with confirmed Covid-19 symptoms in the trial reaches a pre-set level, investigators compare the number in each group to determine whether those who got the vaccine fare significantly better than those who receive the placebo.
As vaccination becomes more widespread, researchers should be able to discern the effect on infection and transmission patterns, although it can be difficult to distinguish the impact of inoculations from that of measures such as lockdowns and mask mandates. The completion of the vaccine trials testing for asymptomatic infections will bring additional information.
Additionally we need to vaccinate more of our population and include those younger than 45 years to rapidly reduce the disease burden in the country. This issue has been addressed by many prominent doctors including Director of AIIMS New Delhi Dr. Randeep Gulleria. Dr. Guleria has said: “We are a very large country and if we were to say that we would want to vaccinate the entire adult population for which the vaccine has been currently approved, then that would mean close to one billion people. We will need two billion doses and there is no way that we could get two billion doses if we have to open it up for everyone.” According to Dr. Guleria, the challenge is to balance the doses available “with the number of people we can vaccinate based on the priority list”. “So what I think one needs to do is to see how the trend is and if you find that after a week or 10 days, the number of people coming for vaccination are falling, open it up for a lower age group and gradually do that. There are people in the lower age group who want to be vaccinated whereas others who are in the older age group meet the criteria but still are reluctant and not willing to take the vaccine but are holding up the line,” he added.
Till date scientists have not been successful in discovering some authentic medicine for complete cure of Covid-19. So we must not be complacent in following SOPs regarding Covid-19, even if we get ourselves vaccinated.
Beware and be safe.
(The author is presently working as Assistant Professor in Muzaffar Nagar Medical College, Utter Pradesh in Preventive & Social Medicine Department)