Both doses key to combat severe symptoms 

  • All vaccines have reduced efficacy against Delta variant  
  • Immune response studies on Pfizer vaccines yet to commence 
  • Single dose of any vaccine likely to be less effective  
  • Single dose of AstraZeneca or Pfizer gives low protection  

By Yumiko Perera 

Since the onset of the Covid-19 vaccination programme in the country, the Allergy, Immunology, and Cell Biology Unit of the Department of Immunology Molecular and Molecular Medicine at the Sri Jayewardenepura University has been carrying out several studies to understand the immune response generated by the vaccines that have been administered to the people in the country.  

Speaking with The Sunday Morning on the progress of the ongoing vaccination studies, Department of Immunology and Molecular Medicine Microbiology Prof. Neelika Malavige stated that the studies primarily focussed on determining how individual immune responses respond to different vaccines, as well as understanding how immune responses to vaccines compare to natural infection, how long such immune responses would last, etc.  

“The studies we conduct also focus on how different vaccines compare to each other, with regard to the immune responses they generate,” Prof. Malavige further noted. 

Speaking on how the vaccines are reacting to the different variants of the virus that are prevalent in the country, Prof. Malavige noted that all vaccines that are currently being administered seem to have reduced efficacy against the Delta variant of the virus and that there isn’t sufficient data available with regard to the Lambda variant in order to draw any conclusions. 

All vaccines being studied

Furthermore, adding that nearly all the vaccines that are being administered across the country at present are being covered in the studies, Prof. Malavige noted that the studies on the immune responses to the Pfizer vaccine, however, are yet to commence.  

“Sri Lanka is a unique country because we have administered so many different types of Covid-19 vaccines across the country, thereby allowing us to be able to compare the immune responses to an array of vaccines, and that too in different age groups and individuals with underlying health problems, as well as pregnancy, etc.,” Prof. Malavige noted. 

According to Prof. Malavige, the studies had initially started with the AstraZeneca Covishield vaccine when it had been administered to healthcare workers in the country. 

She further went on to note that the studies focused on looking at the development of different types of antibody responses, such as the antibody response to different variants, T cell responses, as well as immune memory.  

Antibodies present 16 weeks after first Covishield dose

The studies led by Prof. Malavige and her team, including Prof. Chandima Jeewandara, revealed that even after a single dose of the Covishield AstraZeneca vaccine, 93.4% of individuals had developed antibodies and 97.1% individuals developed neutralising antibodies, whereas 67.1% developed T cell responses.

As this study had been conducted earlier this year (February and March), the antibodies to the Delta variant were not measured, as the variant had not been an issue at the time, Prof. Malavige told The Sunday Morning.  

“We have compared the immune responses of Covishield to natural infection and also looked at antibody responses to Covishield at 16 weeks after a single dose, as there is a large population awaiting the second dose. However, even after 16 weeks, nearly 93.7% had antibodies, but neutralising antibodies had declined in the elderly,” Prof. Malavige noted.  

The study also found that approximately 26.1% of the participants had not generated neutralising antibodies 16 weeks post-vaccination and that antibodies to “Variants of Concern” were not detected, or were very low in all individuals 16 weeks after receiving the first dose of the Covishield vaccine.

However, the participants in the study had shown very good memory T and B cell responses, and therefore, the study further suggests that administering a second dose of the vaccine as soon as possible would boost the immune responses in individuals.

According to Sri Jayewardenepura University Allergy, Immunology, and Cell Biology Unit Director Dr. Chandima Jeewandara, when these individuals are inoculated with the second dose, there is a theoretical possibility that they would produce enough antibodies that would protect them against different variants of the virus, The Sunday Morning learnt.

Speaking to the media earlier this week on the university’s study on the immunogenicity levels of the AstraZeneca vaccine, he elaborated that at 16 weeks, the neutralising antibodies against variants were almost negligible, making individuals susceptible to contracting the newer variants of the virus. 

Furthermore, he also added that a single dose of the AstraZeneca vaccine would give approximately 33% protection, especially against the Delta variant.

Immunogenicity of the Sinopharm vaccine satisfactory

Speaking regarding the most recent study they had conducted with regard to the Sinopharm vaccine, Prof. Malavige noted: “We found that 95% of individuals seroconverted following two doses of the Sinopharm vaccine, while 81.25% developed neutralising antibodies. The antibody levels in those who had received both doses of the vaccine were similar to the levels seen following natural infection of Delta and Beta variants.” 

Noting that the data of the study with regard to the Sinopharm vaccine was released recently, she further mentioned that the data is available as a preprint and that the manuscript is currently under review. 

“Only Pfizer and AstraZeneca have released their efficacy data with regard to the Delta variant so far, and the data shows that one dose of either vaccine gives low protection, but the Pfizer vaccine has shown an 88% efficacy and AstraZeneca has an efficacy rate of 67%,” she noted, further highlighting that these efficacy rates are for symptomatic infection. 

A single dose of any vaccine is likely to be less effective against the Delta variant, Prof. Malavige told The Sunday Morning.  

Vaccination drive progress

According to official data from the Epidemiology Unit of the Ministry of Health, the national vaccination drive against Covid-19 has seen the administration of more than 11.7 million vaccinations thus far, The Sunday Morning learnt.

More than 500,000 vaccinations had been administered for the second consecutive day on 30 July, which marked a significant milestone in the country’s immunisation programme as the highest number of vaccines administered within a day.

As many as 442,253 people received the first dose of the Sinopharm vaccine, while 66,219 individuals had completed the vaccine course, as they were administered with the second dose of the same, The Sunday Morning learnt.

Furthermore, government expenditure on Covid-19 vaccines has amounted to $ 110 million, according to Ministry of Finance and Treasury Secretary S.R. Attygalle.

Meanwhile, according to, Sri Lanka is currently first in the rolling seven-day average per 100 people of the total population who have been vaccinated against Covid-19, and for vaccines that require multiple doses, each individual dose is counted.

Clashing vaccination policies  

While several European Union (EU) countries only accept travellers that have been inoculated with the vaccines that have been authorised by the European Medicines Agency, Sri Lankan workers looking forward to travelling to these countries for employment, are facing a dilemma.  

The European Medicines Agency only allows travellers that have been immunised with vaccines such as Pfizer (Comirnaty), Moderna, AstraZeneca (Vaxzevria), and Johnson & Johnson (Janssen), The Sunday Morning learnt.  

Health Services Deputy Director General Dr. Hemantha Herath told The Sunday Morning that although all the vaccinations that are being used across the island are approved by the World Health Organisation (WHO), different countries have various vaccination policies and they may give priority to certain vaccines over others.  

“If the quality of the vaccines is in question, the WHO would not have approved these vaccines. However, this is a matter of the vaccination policies of various other countries,” he noted.  

Furthermore, during a recent discussion between the Minister of Health and the Minister of Labour, it was agreed to provide the Pfizer Covid vaccine to Sri Lankans travelling for employment. Likewise, on 28 July, the Sri Lanka Bureau of Foreign Employment started administering Covid-19 vaccines, and is expected to inoculate approximately 8,000 Sri Lankan workers that are hoping to travel abroad for employment, under this programme, The Sunday Morning learnt.  

Meanwhile, earlier this month, health authorities of Saudi Arabia had announced that visitors who have received two doses of Sinopharm would be allowed entry into the country, provided they take a booster dose of Pfizer, AstraZeneca, Johnson & Johnson, or Moderna, The Sunday Morning learnt.